Some of the more common skin conditions we see in dogs and cats at the Long Beach Animal Hospital
Sarcoptic mange (cats get a version called notoedric mange ), commonly know as scabies, is caused by an external parasite called Sarcoptes scabei that burrows deep into the skin. It commonly occurs in dogs, not so commonly in cats, unless is it notoedric mange), also occurs in foxes, ferrets, rabbits, sheep, goats, cattle, pigs and guinea pigs.
It is contagious to other pets and occurs in many different animals. It causes intense itchiness, especially affecting the ear margins, elbows, and face. People can pick up this disease from their pet and show symptoms of itching, but it goes away by itself in many cases and usually does not require treatment in most cases (always check with your doctor).
It is important to note that the diagnosis of this skin condition, like most skin conditions, can not be made just by looking at a pet. Diagnostic tests are mandatory to arrive at a correct diagnosis and achieve a satisfactory outcome to therapy. Stating that an animal looks “mangey” is not the same thing as making a positive diagnosis of mange. Pets that have Ringworm , Demodex. and allergies can look like they have Sarcoptic mange.
This ectoparasite spends it life cycle of 14-21 days entirely on the host it has infected. Overcrowded conditions increase risk for transmission.
The following history for an itching pet with sarcoptes usually involves:
In dogs most of the symptoms involve intense itching at the ear margins, elbows, hocks and abdomen. Less common areas of itching can include the face and feet. This itching will inflame the skin and cause scabs with a secondary bacterial infection (pyoderma) occurring due to the trauma. Some pets will shake their ears excessively and cause an aural hematoma (swollen ear). These symptoms can mimic those of other skin conditions, so the rules of the diagnostic process should be carefully adhered to.
Other symptoms that might be present sometimes include:
In cats, sarcoptic mange is caused by a mite called notoedres cati, a microscopic ectoparasite that burrows in to the skin. It is not as itchy, and occurs more often on the face, ears, paws, and tail.
This is a highly magnified view of notoedres cati as it appears under the microscope
This cat has scabies, but you can’t say that for sure just by looking at it.
The top of his head shows how irritating the problem is, especially at the ears.
The primary way to diagnose sarcoptic mange is to do a skin scraping where the patches of alopecia occur. Finding these mites, their eggs, or their feces, under the microscope can be very difficult in this disease. a pet that has the symptoms of Sarcoptic mange and is negative on skin scrapings for the parasite can still have the disease. In these cases we commonly treat for the disease anyway, because the treatment is highly effective.
In rare cases we will do a skin biopsy, which is a great way to rule out other diseases that have similar symptoms.
Other diseases in dogs that mimic scabies include:
Diseases in cats that mimic scabies include:
The usual treatment for Sarcoptic mange is a drug called Ivermectin. It is an injection given weekly for up to 6 weeks. Most pets decrease their scratching rapidly after the first injection. Some dogs, particularly Collies, Shetland Sheepdogs, and Old English Sheepdogs do not tolerate the medication well. In these pets we use a dip called Lyme Sulfur that is also very effective. The disadvantage to the dip is the odor it causes and the staining of white coated animals. All pets in a household should be treated regardless of whether they are showing symptoms or not. Pets that have secondary skin infections from the trauma might also be put on antibiotics. Other common treatments include Revolution (selamectin) topical.
Other pets in the same household are commonly treated if they are in close contact. Treating the environment is usually not needed if all pets in the house are treated.
Some pets itch more in the first few days of treatment due to dying mites. These pets can be put on cortisone in a reducing dose to get over this phase.
This dog has scabies
This is a picture from the dog above 7 days after its first Ivermectin injection
Good nutrition and plenty of play and exercise are always important to maintain the proper balance to fight off disease. All pets in a household that has a pet diagnosed with this disease should also be treated.
Cushing’s Disease (also known as hyperadrenocorticism- Cushing’s is easier to pronounce, so stick with that word) results when the adrenal glands secrete an excess amount of cortisone. It is the most common endocrinopathy (hormone disease) encountered in older dogs. This disease is the exact opposite of another endocrine problem in dogs called Addison’s disease (hypoadrenocorticism).
This detailed page will emphasize Cushing’s disease in dogs, with an explanation of how it differs from cats at the end. This is a complex hormonal disease that does not lend itself to a simple explanation or an easy diagnosis. Some pets have the symptoms, yet the tests are negative. Other pets have positive test results, but minimal symptoms that do not warrant treatment. Pace yourself-you might want to go to the bathroom before attempting this page!
We have a summary page on Cushing’s if the explanation on this page is too detailed for your needs.
The adrenal glands are small, so click on photos to enlarge them.
Several medical terms and abbreviations relate directly to Cushing’s:
|cortisol– cortisone produced by the adrenal glands||atrophy– decreased size of an organ|
|exogenous cortisone– supplemental cortisone||hypertrophy– increased size of an organ|
|HAC – hyperadrenocorticism||polyuria– excess urinating|
|CRH– corticotropin releasing hormone||polydipsia– excess drinking|
|polyphagia– excess appetite||PU/PD– polyuria and polydipsia|
|glucocorticoids– mostly cortisol, and a small amount of cortisone||mineralcorticoid-hormone that affects sodium and potassium|
|hypoglycemia– low blood glucose level||iatrogenic– caused by something a person does as opposed to happening naturally.|
|adrenalectomy– surgery to remove the adrenal gland.||ACTH– adrenocorticotrophic hormone|
|hepatomegaly– enlarged liver||adrenomegaly– enlarged adrenal gland|
|anabolic steroid– testosterone and its equivalent||PD– pituitary dependent|
|catabolic steroid– cortisol and its equivalent||AT– adrenal tumor|
The adrenal glands are small paired glands buried in fat in the front of each kidney. Even though they are small, the cortisol they secrete, along with their other functions, have great significance to normal physiology. These guys are small but mighty, as you are about to learn!
The arrows point to the paired adrenal glands in front of each kidney. The extensive blood supply to the kidneys and adrenal glands is apparent. In the diagram they are easy to see. They are not so easy to see during ultrasound or exploratory surgery because normally they are small and buried in fat. They do not show up on an X-ray unless they are calcified.
A normal adrenal gland of a dog buried in fat just above the kidney. The white structure is the tiny adrenal gland, the dark structure below it is called the Phrenicoabdominal vein. It is a large vein for such a tiny organ, a testament to the importance of the adrenal gland.
This is a normal ferret right adrenal gland, just under a lobe of the liver, which is pulled forward by the surgeon’s fingers
This is a normal ferret left adrenal gland (just above the hemostat) buried in fat. The left kidney is the structure to the right.
This is a picture of an enlarged left adrenal gland (arrow) that is buried in fat near the kidney (K). I is from a ferret that has adrenal gland tumor, so the gland is inflamed and easy to visualize. This is not necessarily the case in dog and cats with adrenal gland tumors.
The internal architecture of the adrenal gland is made up of several distinct zones.
The cortex (outer shell) of the adrenal gland is made up of 3 anatomical parts:
This is the outer layer of the adrenal gland. This section secretes the mineralcorticoid aldosterone. Aldosterone is vital to proper sodium and potassium regulation. Aldosterone has a role in maintaining blood pressure.
This is the next layer as you go inward, and produces the glucocorticoid cortisol. The cells in this area are the ones that cause Cushing’s.
As we continue inward we come across this section that secretes the sex hormones known as androgens (male sex hormones), estrogen (female sex hormones), and sex steroids. These are usually secreted in such small amounts as to be of no major significance in healthy animals.
This consists of the very center of the adrenal gland. It secretes hormones called catecholamines. The two important ones are epinephrine (adrenaline) and norepinephrine.
These tiny organs have a profound influence on many internal organs. The hormones they secrete work in unison with other internal organs, particularly the liver, and have an enormous effect on physiology. These hormones interact with many other hormones that have the opposite effect, usually in some type of feedback mechanism that is monitored by the brain. This interaction is complex, so only a summary of adrenal hormone physiology is presented.
The adrenal glands secrete several important hormones, most of which are synthesized from cholesterol. We will explain 3 of them; cortisol, aldosterone, and epinephrine:
Cortisol is a hormone that is essential for life. Cortisol maintains a normal blood glucose level, facilitates metabolism of fat, and supports the vascular and nervous systems. It affects the skeletal muscles, the red blood cell production system, the immune system, and the kidneys.
It is considered a “catabolic steroid”. This means it takes amino acids from the skeletal muscles and, with help from the liver, converts them to glycogen, the storage form of glucose. These functions are the exact opposite of “anabolic steroids”, the drugs that weight lifters take to increase muscle mass. The end result of this is an increase in the level of glucose in the bloodstream. The hormone called insulin has the opposite effect on blood glucose, adding to the complexity of this system. You can learn more about insulin by going to our diabetes mellitus page.
The level of cortisol in the bloodstream continually fluctuates as physiologic needs vary. Surgery, infection, stress, fever, and hypoglycemia (low blood sugar) will cause cortisol to increase. This continual fluctuation adds to the difficulty of diagnosing Cushing’s, because the amount of cortisol in the bloodstream is so variable. A test taken at one moment in time might have different results if taken later.
To control the level of cortisol the hypothalamus and pituitary gland in the brain secrete chemicals into the bloodstream called releasing factors. In the case of the adrenal glands , the hypothalamus secretes a hormone called corticotropin releasing hormone (CRH). It goes to the pituitary gland and stimulates it to release a hormone called adrenocorticotrophic hormone (ACTH). It is the amount of ACTH circulating in the blood stream that tells the adrenal glands (specifically, the cells at the zona fasciculata) how much cortisol to secrete. There is a negative feedback loop that allows the hypothalamus and pituitary gland to refine precisely how much cortisol circulates in the bloodstream. The more cortisol secreted by the adrenal glands, the less CRH and ACTH secreted. This allows the body to precisely refine the level of cortisol, and to change the level rapidly due to changing physiologic needs.
Numerous internal organs are affected by cortisol:
Cortisol is needed for proper muscle action, yet too much can cause the muscles to atrophy (shrink). This is due to their catabolic effect. This means that they literally cause the body to break down the amino acids in the muscle fibers in order to increase the blood glucose (sugar) level. Cortisol does this in a complex mechanism that involves the liver. The end result is the muscles become smaller. When this occurs at the abdominal muscles the abdomen appears pot bellied.
Bone is made up of a protein matrix and calcium, both of which are affected by cortisol. Excess cortisol affects the protein matrix, decreases calcium absorption from the intestines, and increases calcium excretion by the kidneys. Skeletal mass decreases and bones become weaker.
It causes atrophy of hair follicles and sebaceous glands, which leads to alopecia (hair loss). Elastic tissue under the skin is also affected, leading to thinner skin and adding to the pendulous abdomen. The disruption in the elastic tissue of the skin can also cause calcium changes in the skin. This might lead to areas where calcium builds up in small nodules. In cats the skin changes can become severe, and are referred to as fragile skin syndrome.
Cortisol is required for maintaining the integrity of the lining of blood vessels. An excess will lead to thinning of these walls and the potential for rupture. The end result is a hematoma. Cortisol also increases the number of circulating red blood cells and helps maintain blood pressure.
Cortisol is necessary for the normal maintenance of brain functions. It can interfere with sleep and change the mood. You might notice these effects if your dog has Cushing’s or is given supplemental cortisone for treatment of a disease.
Excess cortisol will increase the workload on the liver as it converts amino acids to glycogen. Pets with Cushing’s will commonly have an enlarged liver, known as hepatomegaly. You will be shown a picture of an enlarged liver on an x-ray in the diagnosis section.
An increase of cortisol increases the blood flow (also called GFR-glomerular filtration rate) to the kidneys. This will result in an increase in the amount of water and waste products filtered by the kidneys. Our kidney disease page has more details. This is one of the reasons why dogs with Cushing’s drink and urinate excessively (PU/PD), and urinate a dilute urine.
This is one of the more profound functions of cortisol. It decreases the inflammatory process and helps minimize an over reaction of the immune system to foreign bodies or infections. Unfortunately, it also suppresses the immune system to the point that the body has a hard time mounting a proper response. The body is more susceptible to infections, especially those caused by bacteria. This is one of the reasons why we routinely prescribe antibiotics when we prescribe cortisone if we suspect any type of bacterial or fungal infection.
Aldosterone is the principal mineralcorticoid secreted by the adrenal glands. This hormone is secreted as a response from the kidneys when fluid volume in the bloodstream is decreasing. It involves other hormones called renin and angiotensin. The end result is an increase in sodium in the bloodstream, with a corresponding increase in blood volume and blood pressure. This hormone also interacts with and affects potassium levels. To further complicate the picture, ACTH also has an affect here, just like it does with cortisol.
This part of adrenal gland physiology is not significantly altered in Cushing’s. Addison’s disease, which is the production of too little cortisone, has a greater affect on aldosterone.
This compound, technically called a neurotransmitter, also has hormone-like properties. It is a very powerful chemical that effects all organ systems. It acts very rapidly, with effects remaining only for a short period of time. It is the primary reason the body has the ability to respond to an emergency. This physiologic mechanism is also known as the “flight or fight” response.
Upon stimulation of the central nervous system (ex.-fear or pain), the adrenal medulla is stimulated to secrete epinephrine into the bloodstream. We are all familiar with what happens next. The pupils dilate, the heart rate and blood pressure increase, and the palms get sweaty. Internally, the body is increasing the blood glucose level, the breathing passages are opened up, more red blood cells are secreted into the circulation, blood is shunted away from the skin and other internal organs, and blood flow is increased to the brain and skeletal muscles. All of this has the effect of bringing the brain and skeletal muscles extra glucose and oxygen, and accounts for the extra boost of awareness and energy we all feel at this time.
Up to 85% of all Cushing’s cases in dogs fall into this category. The pituitary gland is invaded with a slow growing cancer called an adenoma. This causes it to secrete an excess amount of ACTH. The cells in the zona fasciculata area of the adrenal glands respond to this excess ACTH by hypertrophying (enlarging) and secreting excess cortisol. It is this excess of cortisol that is circulating in the bloodstream that causes the symptoms we see in this disease.
This pituitary gland tumor can remain slow growing and not effect the pet any more than inducing Cushing’s disease. In 10-20% of these tumors they enlarge to the point that they will cause significant neurologic symptoms. Unfortunately, some of these neurologic symptoms mimic those seen as side effects to the medication used to treat Cushing’s.
Brain tumors are best diagnosed using an MRI (magnetic resonance imaging). This boxer has a large white tumor in its brain.
In up to 15% percent of Cushing’s there is an actual tumor of one of the adrenal glands (sometimes both are involved). The tumor enlarges and secretes excess cortisol in the bloodstream. This excess cortisol is monitored by the hypothalamus and pituitary in the negative feedback mechanism, causing them to secrete less ACTH. Less ACTH in the bloodstream will cause the other adrenal (if it does not also have a tumor) to atrophy (shrink).
The benign version of this tumor occurs 50% of the time, and is called an adenoma. The malignant version, which occurs the other 50% of the time, is called an adenocarcinoma. It can invade the primary vein returning blood back to the heart (called the vena cava), and spread from the adrenal gland to the liver, lung, kidney, and lymph nodes.
The white arrow points to a small and normal right adrenal gland in a ferret. A lobe of the liver has been pulled forward so you can see the adrenal gland. The dark blue structure running horizontally is the vena cava (VC)as it coarses past the liver towards the heart. The close proximity of the adrenal to the vena cava and liver shows how easily a malignant tumor here can spread into the bloodstream and lodge elsewhere in the body.
This is a very large right adrenal tumor, almost as large (and intertwined) as the kidney below it. Notice how the vena cava (dark blue vertical structure to the right of the tumor) goes in a different direction that the pictures above. Removing it is not possible without also removing the vena cava.
This chest radiograph follows the vena cava (arrows) as it passes through the diaphragm and continues from the liver to the heart. Unfortunately, the heart unwittingly can now pump cancerous tissue to the rest of the body.
Adrenal tumors are a common problem in ferrets. The adrenal tumor in this case does not secrete excess cortisol, so technically the disease is not called Cushing’s. The tumor causes an excess secretion of sex hormones, causing a different set of symptoms when compared to the dog and cat.
Exogenous (external or supplemental) use of cortisone is very common in medicine. It is a highly beneficial drug used to treat a wide variety of diseases. In some cases it is used as an emergency drug to literally save a life. Cortisone is beneficial in several disease categories:
Long term use of cortisone, in oral, injectable, or even topical form, might cause an animal to have the symptoms of Cushing’s disease. It all depends on the type of cortisone used, the dose it is used at, and the duration of use. As a general rule, once the original symptoms of the disease are treated with cortisone, we recommend decreasing its use, stopping its use, or finding an alternative drug. Sometimes this is not feasible though, especially in immune system diseases. The symptoms of these diseases far outweigh the potential side effects from this exogenous use of cortisone.
The level of cortisone that results from this exogenous use will cause the adrenal glands to atrophy. The negative feedback loop tells the brain there is plenty of cortisol in the bloodstream, so the pituitary secretes less ACTH. The pet has the symptoms of Cushing’s because cortisone is being introduced into its body, not because the adrenal glands are producing it in excess amounts.
Exogenous cortisone goes by several names. They come in injectable, oral, and topical forms, and tend to be more potent than the cortisol that is naturally produced by the adrenal glands. Some of the more common ones are:
This is a rare version of Cushing’s that does not fall into any of the above categories. It can be found in association with cancer in the dog.
Some dogs with Cushing’s disease show the classic symptoms, while other show only a few vague symptoms. The classic symptoms are:
A thorough approach is needed for a correct diagnosis of Cushing’s. In every disease we encounter we follow the tenet’s of the diagnostic approach to ensure that we make an accurate diagnosis, and also so that we do not overlook some of the other diseases that are common in pets as they age. Nature works in complex ways, and just because you have one disease does not mean you cannot get another one to complicate the matter.
The best way to diagnose this disease is with history and physical exam. If your dog has PU/PD, polyphagia, alopecia, muscle weakness, and excessive panting, then it most likely has Cushing’s. The adrenal screening tests are used to verify the diagnosis.
Some dogs have the normal symptoms of Cushing’s, but routine blood sampling does not bear this out. In these cases we will repeat the adrenal screening tests at some time in the future or even abdominal ultrasound to look at the actual glands.
Cushing’s tends to be a problem that affects older dogs, usually greater than 6 years of age, with a median age of onset at around 10 years. The disease tends to have a slow and gradual onset, so the early symptoms are easily missed.
Several canine breeds are prone to getting Cushing’s:
Females and males get it at about the same frequency. Neutered pets might be at higher risk of Cushing’s.
Cushing’s disease is suspected in any pet that has some of the symptoms described above, particularly the skin symptoms and the PU/PD. It is important to remember that some dogs do not show any symptoms early in the course of the disease. This is another reason for yearly exams and blood and urine samples in dogs and cats 8 years of age or more.
Since dogs with this disease do not have a poor appetite usually (they have the opposite as explained in the symptoms section above), owners will delay in bringing their dog in for an exam. They assume a good appetite means their dog is doing fine. They misinterpret the excessive appetite (polyphagia) as being a good sign, when in reality its a sign of disease.
Most people wait until a dog, that is normally housebroken, is now urinating in the house. This delay can make it difficult to treat, and will frustrate some people to the point they are contemplating euthanasia.
Other historical findings include skin infections that recur after antibiotic therapy is stopped. Some dogs have a history of pruritis (itchiness) if pyoderma is present.
A history of poorly controlled diabetes mellitus might also clue us in to Cushing’s.
Routine physical exam findings might include:
Several tests are used as an aid in making this diagnosis. Each test has its advantages and disadvantages.
Skin scrapings are usually negative in Cushing’s, although demodex is possible as a secondary problem due to the immunosupression effect of cortisol. Long term use of cortisone orally can also predispose a pet to demodex due to its immunosuppressive effects.
A CBC (complete blood count) and biochemistry panel should be run on every dog 8 years of age or more, especially if they have any of the symptoms of Cushing’s.
The CBC might show an increase in the number of red blood cells (RBC’s) and/or an increase in platelets (thrombocytosis). It might also show an increased WBC (white blood cell count), called leukocytosis. When these white blood cells are broken down, there are usually more neutrophils (neutrophilia), less lymphocytes (lymphopenia), and less eosinophils (eosinopenia). These white blood cell abnormalities can also be caused by the “stress response”. It is due to excess epinephrine and cortisol secreted in response to the actual process of taking the blood sample (those people that have passed out when their blood was taken are an extreme example of this). The excess cortisol secreted by the adrenals in the stress response is temporary, and part of normal physiology. It is not caused by Cushing’s disease.
Cholesterol, blood glucose. triglycerides, and liver enzyme tests (ALT) might be elevated in Cushing’s. If a thyroid test is run it might be low or borderline normal.
An elevated alkaline phosphatase (Alk Phos) is a consistent finding in Cushing’s. This is an enzyme that is located in the bile production area of the liver. The excess cortisol influences this enzyme, although growing animals, fractures, obstructions of the bile ducts, liver disease, drugs, pets with diabetes mellitus, and pets with cancer can all cause an elevated Alk Phos. A significantly increased Alk Phos alerts us to keep Cushing’s in our tentative diagnosis list.
This dog has a mildly elevated liver enzyme test and am elevated Alk Phos. If the signalment, history, and physical exam do not make us suspect Cushing’s we probably will not proceed to adrenal screening tests. This dog should be examined, and the blood should be checked every 3-6 months to see if these abnormalities are increasing.
This dog with Cushing’s has several problems on the blood panel that are secondary to the Cushing’s:
Increased WBC- 23.7
Severely increased liver enzymes- Alk Phos- 5224
Low thyroid- <0.5
Low urine Specific Gravity- 1.008
This is the blood panel on the same dog with Cushing’s two weeks after starting treatment. The WBC’s are back to normal, and the Alk Phos is much less. As time we goes on and we continue treatment we can expect these values to continue to improve.
A normal specific gravity in a dog should be at least 1.025, and there should be no or minimal protein, glucose, WBC’s, or bacteria, as a general rule. With Cushing’s, the specific gravity of the urine might be low, the protein might be elevated, and a urinary tract infection might be present because of excess glucose in the urine.
This urinalysis of this dog shows a low specific gravity, which is consistent with Cushing’s
This test can give us an idea that Cushing’s is the cause of a skin problem. Many of the changes that are noted microscopically when evaluating the biopsy are also seen in other diseases, so it is not specific for Cushing’s. In spite of this fact, skin biopsies give us a large amount of information in skin conditions.
Radiography might be of value if the adrenal glands are calcified (happens in up to 50% of adrenal tumors), otherwise the adrenals do not show up on a radiograph. Hepatomegaly can be seen on the radiograph, along with problems associated with other diseases in pets this age, so a radiograph can be highly beneficial to help rule them out. Radiography might also show osteoporosis (poor bone density) and calcification of soft tissue, both of which could be due to excess cortisol.
In this lateral view (laying on its side) of the abdomen, the kidney (K) closest to the arrow is the right kidney. The arrow points to where the right adrenal gland is located, although it cannot be seen since it is not calcified. The whitish area between the K’s is normal, and is caused by the effect of the 2 kidneys as they overlap.
This is a VD (ventral-dorsal, or laying on its back) view of a dog. The left kidney (K) is labeled, and the arrow points to where the left adrenal gland is located. There is some calcification in this radiograph, but it is not at the adrenal gland. Can you see it?
The liver (L) might be enlarged (hepatomegaly), although this enlargement can be found in other diseases, especially liver cancer and diabetes mellitus
This test can be highly beneficial in this diagnosis. The adrenal glands can be measured, and their internal architecture (called parenchyma) can be analyzed. It is not feasible to visualize all of the distinct different zones of the adrenal gland though. Other internal organs are also checked, giving us a substantial amount of information from just one test. A common incidental finding when we do a routine ultrasound on a dog suspected of having Cushing’s is to find this pet also has IBD (Inflammatory Bowel Disease).
This is the report
This is the most reliable way to confirm a diagnosis of Cushing’s disease. These tests evaluate the interactions that are occurring between the hypothalamus, the pituitary gland, and the adrenal gland. The interaction between these glands is known as the hypothalmic-pituitary-adrenal axis. The first goal is to determine if Cushing’s disease exists. The next step is to determine if it is pituitary dependent (PD) or non-pituitary dependent (an adrenal tumor- AT). You might want to go back to the Cause Section above for a review before proceeding further.
Testing this axis is not as easy as it sounds. The mammalian body is a dynamic system with thousands of chemical reactions and interactions occurring simultaneously. Also, levels of cortisol are in a continual state of flux, depending on the time of day, the season, medications, diet, and stress levels. Underlying diseases like Urinary Tract Infections can affect these screening tests, and need to be controlled first. Because of all this variability, interpreting these tests can be problematic, and it is not uncommon to repeat them in the future to look for consistent findings and monitor trends.
We prefer to perform these tests when the stress level (for example a car ride to our hospital) is not high. It might be worth it to take your dog for a short walk after you park the car to let it settle down. One of the rests requires a 8 hour hospital stay.
The normal values in animals calculated by a particular lab are called reference values. They reflect 95% of the population, statistically the same thing as the values that fall under the bell shaped curve. Not every animal falls perfectly into this range, so there is always a degree of interpretation needed in determining whether a value is abnormal or not. Eventually, it boils down to a determination of probabilities, coupled with experience in diagnosing diseases in animals.
Sometimes the test results are borderline for the disease. In these cases we use other test like ultrasounds, or we repeat the tests 1-3 month down the road.
Two important concepts of laboratory testing relate directly to Cushing’s:
The sensitivity of a test refers to the ability of that test to detect diseased patients. A Cushing’s test that is 95% sensitive will diagnose Cushing’s in 95% of all dogs with Cushing’s disease. 5% of the dogs in this scenario will have Cushing’s, even though their screening test for Cushing’s says they don’t have the disease.
The specificity of a test refers to the ability of the test to detect only diseased patients. A Cushing’s test that is 95% specific means that 95% of the time if the test is positive for Cushing’s, the animal really does have Cushing’s. This means that 5% of the time the test will say an animal has Cushing’s disease when in reality it does not.
Animals that do not have Cushing’s disease might show up positive on these tests, while others that have the disease might be negative on these tests. Many times we have to play the odds based on probabilities. Due to this limitation in testing we recommend using these tests in combination, and repeating them if they do not give clear cut answers.
These tests sometimes come back as positive for Cushing’s when in reality other diseases are affecting the cortisol level. Some of these diseases (called non adrenal illness) include liver disease, chronic kidney disease, urinary tract infection, skin diseases, and uncontrolled diabetes mellitus. Also, cortisone and anticonvulsants can give false positives.
The most common screening tests are as follows. Now might be a good time to take that bathroom break before reading about these tests.
In this test the level of cortisol in the urine is measured and used as an indication of the cortisol level in the bloodstream. Creatinine is measured to adjust for different levels of urine dilution. Our kidney page has more information on creatinine.
This test is useful as a screening tool when our differential diagnosis (you know what that means because you read theDiagnostic Process page) does not put Cushing’s on the top of the list. For example, we might use it in a pet that has PU/PD, but not the other signs of Cushing’s. It works in both dogs and cats.
This one came back positive, which means this dog might have Cushing’s, and it warrants further testing to confirm. If it was negative, we would probably not do any further testing for Cushing’s, unless we felt the test was improperly obtained, or the dog had significant symptoms of Cushing’s.
This test is easy to perform because all that is needed is a urine sample. We recommend you obtain this sample at home in the morning just after your pet wakes up. Bring it to us immediately for analysis by our lab. Obtaining it at home will minimize the stress of a car ride and a visit to our hospital, both of which will normally increase the level of cortisol in the bloodstream (remember the stress response?), thus affecting this test.
A high level of cortisol in the sample is suggestive of Cushing’s. Unfortunately, up to 80% of dogs that don’t have Cushing’s will also have an increased level. This means that the specificity is low. If the cortisol:creatinine test comes back normal, then it is unlikely that Cushing’s is present, and we do not routinely recommend the following screening tests. A cortisol:creatinine ratio test that is high means Cushing’s might be present, and needs one of the other screening tests to determine if Cushing’s is indeed present.
This test checks for Cushing’s and Addison’s Disease. We tend to use this screening test when we suspect Iatrogenic Cushing’s. It is also used to monitor therapy on pet that is on medication for Cushing’s and Addison’s disease.
When a dog or cat is given ACTH by an injection the adrenal glands are stimulated to produce cortisol. By measuring this cortisol with a blood sample we can determine what reserve the adrenal glands have in the production of cortisol.
This is what we use for the ACTH stimulation test
This test is very specific for Cushing’s, so false positives are rare compared to other screening tests. It is not as sensitive as other screening tests, particularly the LDDS test. For this reason it is sometimes used in combination with the LDDS test.
This dog does not have Cushing’s according to this test, but it might also be a false negative if the symptoms of Cushing’s are present
This is the only test that can distinguish between iatrogenic and naturally occurring Cushing’s. It is the only test that gives reliable results for a dog that has been on cortisone recently. It does not distinguish between pituitary dependent (PD) and non-pituitary dependent (AT-adrenal tumor).
A blood sample is taken to measure the resting cortisol level before ACTH is given. Two hours after the ACTH injection is given a blood sample is taken again to measure the level of cortisol. This two hours gives the ACTH injection time to stimulate the adrenal glands to produce cortisol.
In the dog, if the second test of cortisol is much higher than the first, it is suggestive of Cushing’s 80-95% of the time. It does not necessarily tell us if it is PD or AT, because this exaggerated response will occur in 85% of PD Cushing’s, and also 50% of those with AT Cushing’s. This test is not as reliable in cats, only 51% of cats with Cushing’s will show an exaggerated response.
If there is a reduced level of cortisol on the second blood sample, then either the dog has Addison’s disease or iatrogenic Cushing’s. This reduced response also occurs in dogs that are receiving Mitotane or Ketaconazole therapy for Cushing’s.
Between 5% and 20% of dogs that have Cushing’s (either PD or AT) will not show the exaggerated response expected with this disease. If this test is normal or borderline in a dog we suspect Cushing’s in these dogs then the test should be repeated at a later date, or the LDDS test should be performed.
This is probably the best test when the history, physical exam, and routine blood panel and urinalysis are consistent with Cushing’s. We also use it when we feel there is no chance of Iatrogenic Cushing’s. It might also help differentiate between PDH and AT, but that is better determined by the HDDS test (High Dose Dexamethasone Suppression test). It only works in dogs because cats get a significant number of false positives.
It is sensitive for Cushing’s because 85% to 100% of the time it finds a Cushing’s disease that is present. Its specificity is low though, meaning it might come back as positive for Cushing’s between 44% and 73% of the time when the dog does not have Cushing’s. If we are not sure of the results because of this variability, we might also perform an ACTH stimulate test.
This dose of dexamethasone (which is a version of cortisone) suppresses the adrenal gland from producing cortisol in normal dogs, but not those with Cushing’s. It achieves this suppression by interfering with the negative feedback mechanism. The dexamethasone is monitored by the brain as an excess of cortisone in the bloodstream, so less ACTH is secreted, and therefore less cortisol is secreted by the adrenal gland.
In this test an injection of Dexamethasone is given and cortisol levels are measured at 4 hours and 8 hours after the injection. Like the ACTH stimulation test, a pre-injection blood sample is taken to measure the resting cortisol level.
Here are the LDDS test results on a dog that we suspected of having Cushing’s. What is your diagnosis in this case? It’s the same dog that had the ultrasound above.
This test is not used as a routine screening test. It comes into play when a dog already has Cushing’s and you want to be certain that it is not that rare case that is an adrenal tumor.
The protocol for this test is similar to the LDDS test, except of course, a higher dose of dexamethasone is injected. A dog with an adrenal tumor does not suppress cortisol levels from the baseline sample.
In some dogs with Cushing’s the excess cortisol that circulates in the blood stream will spill over into the urine. If this test is positive then a dog might have Cushing’s. If it is negative, there is a good chance it does not have Cushing’s.
A positive on this test gives a reasonably good chance that a dog has Cushing’s. It will not catch all dogs with Cushing’s, so a dog with a negative test might still have the disease. In general, we use this test to monitor patients that are already being treated for Cushing’s or Addison’s.
This test will catch most dogs that have the disease, and is the test of choice for Cushing’s on dogs that have symptoms. A negative on this test means that most likely the dog does not have Cushing’s. A positive on this test indicates that a dog might have Cushing’s. It is the most popular adrenal screening test.
One of the tenets of the diagnostic process is whether or not a treatment that is instituted actually corrects the problem. This usually applies to Cushing’s. You should note significantly less PU/PD, improved skin, and a more active pet if the treatment is successful.
Before we discuss treatment we need to keep things in perspective. This is a chronic disease, and most dogs do not die from this disease. We tend to treat when the symptoms described previously are affecting a dog’s quality of life or are a major nuisance to a pet owner. We do not routinely treat just because the tests say your dog has Cushing’s- the symptoms of the disease need to be present also. Dogs that have significant symptoms of Cushings’ that have been confirmed by screening tests need to be treated to prevent potentially serious diseases secondary to Cushing’s that include Diabetes Mellitus, Urinary Tract Infection (UTI), pancreatitis and High Blood Pressure (Hypertension).
To know if there is a Urinary Tract Infection a culture of the urine must be performed. This dog is negative for a UTI
Treatment can be drawn out, and involves significant time and expense to monitor your pet after we treat it. Also, in some dogs, treatment can lead to side effects that are more serious than the symptoms of this disease. One of these side effects includes a rare death, so we do not undertake treatment of this disease lightly.
This disease tends to occur in older dogs that commonly have other problems. Some dogs die of other diseases before the symptoms of Cushing’s become a significant problem. Treating Cushing’s does not necessarily give your pet a longer life. The goal of therapy is to give your pet a better quality of life.
Underlying problems need identification and treatment. The biggest underlying, overlooked, and serious problem we commonly find in dog with Cushing’s is Dental Disease. If your dog is hypothyroid the problem needs to be corrected with supplemental soloxine. Internal organ problems like kidney disease and liver disease need treatment for a successful Cushing’s outcome. Urinary tract and skin infections need to be cleared up with the use of antibiotics, and underlying diabetes mellitus needs to be regulated with insulin.
Some dogs with large tumors of the pituitary gland might initially respond to medical therapy for pituitary dependent Cushing’s. The Cushing’s symptoms, especially neurologic, might recur as the tumor progresses.
Several different treatment modalities have been developed for Cushing’s. Some are for Pituitary Dependent Cushing’s, some are for Iatrogenic Cushing’s, and some are for adrenal tumors.
This is the newest treatment for this disease, and the one we recommend in most cases. Trilostane is an inhibitor of an enzyme called 3-beta-hydroxysteroid dehydrogenase. This enzyme is involved in the production of several steroids including cortisol. Inhibiting this enzyme inhibits the production of cortisol.
It will be given daily for the rest of your dog’s life
It is usually given once per day, but in some dogs, especially those with Diabetes Mellitus, the Cushing’s symptoms might not diminish at the once daily dosing and the medication needs to be given twice per day (every 12 hours).
When we use this drug to treat your dog’s Cushing’s we will also give you a detailed flow chart of what to look for at home and when to return for additional test and monitoring
This drug has been used to treat this disease for 30 years, and is know by the trade name of Lysodren. It selectively destroys the zona fasciculata and reticularis, effectively limiting the amount of cortisol that these areas of the adrenal gland can secrete. Pets that are on insulin for diabetes mellitus need to have their mitotane and insulin doses adjusted downwards. It should be administered with meals to enhance its absorption. This drug is first administered at a loading dose for 7-10 days.
Side effects are not uncommon:
Side effects are due to the cortisol level being reduced below normal levels. Even if the cortisol level does not go below normal levels, a rapid decrease in elevated cortisol levels to the normal range can still cause these symptoms.
You need to closely observe your pet when it is on mitotane for any of the above side effects. If they occur you are to immediately stop medicating and call us. We will already have given you prednisone pills to give at home if side effects are significant.
After 7-10 days of loading dose the cortisol levels are assessed with the ACTH stimulation test. Do not give your pet any supplemental cortisone on the day of testing. The pre and post cortisol levels should be normal. If they are, then we will continue to use mitotane at a weekly maintenance dose to prevent the problem from recurring again. Once your pet gets to this point it is rare to need any supplemental cortisone pills.
Two long term effects can occur while on mitotane maintenance therapy:
This drug controls the symptoms of Cushing’s 80% of the time.
This is a drug routinely used to control fungal infections. It has a different mechanism of action than mitotane. It inhibits cortisol production in dogs and humanoids by preventing enzyme pathways from functioning properly. Ketaconazole works for PD and AT Cushing’s. It is not as common to use as the previous 2 drugs.
It needs to be given at a test dose initially to watch for anorexia or emesis. If tolerated well, a loading dose is given for 7-10 days. After an ACTH test to determine if the cortisol is in the normal range, the drug is given every 12 hours for the rest of the dogs life. This is a more expensive proposition than mitotane.
Surgery to remove both adrenal glands can also be used. It is an involved endeavor performed at a specialized surgical hospital. Post operative complications are common, and these pets need lifetime prednisone replacement therapy. As a result, this treatment is not commonly utilized.
Recurrence of the symptoms of PD Cushing’s after initiation of therapy might be an indication of a large pituitary tumor. MRI is recommended to identify this type of tumor. Radiation therapy is recommended to prevent further progression of symptoms. Unfortunately, there are very few specialty radiation centers that can perform this procedure.
This form of Cushing’s is the easiest to treat since we are not giving a medication but taking one away. In most cases the elimination of exogenous cortisone will return your pet to normal function, although this might take several months. Some of the skin changes might take longer, and may not even return completely to normal. In some cases we use a decreasing dose of supplemental prednisone for several weeks to give the adrenal glands time to resume normal production of cortisol.
The surgery to remove the cancerous adrenal gland is called an adrenalectomy. It is a specialized surgery that is not routinely performed. Post operative complications are common.
Because the remaining adrenal gland is atrophied the dog needs to be supplemented with prednisone until the gland returns to normal function. ACTH tests are done every few months to determine when the gland is functioning normally, which can take up to 12 months.
Adrenal tumors can also be treated with mitotane at high doses and for a long period of time. Side effects are common at this dose, and relapses can occur. These dogs will also need to be on supplemental prednisone for the rest of their lives.
Cushing’s in cats is rare compared to dogs. One reason is because they tend to be more resistant to higher levels of cortisol, especially if iatrogenic. Most feline Cushing’s occurs in females. It can affect the ability to control the blood sugar level in cats with diabetes mellitus concurrently.
Cats do not show as much PU/PD as dogs do, unless they have diabetes mellitus concurrently. Most cats are presented in a more advanced state of Cushing’s disease because the early symptom of PU/PD is not observed. They might also have hepatomegaly, weight gain, pot-bellied appearance, and muscle wasting. Sometimes the skin is easily bruised and torn. This is called the fragile skin syndrome.
This picture is from an older cat that was at the groomer to be clipped. The skin literally peeled off like wet tissue paper when the groomer attempted to clip some mats. This is a serious problem and does not lend itself to easy treatment.
Cats do not routinely show any changes on a regular blood panel or urinalysis. The most consistent finding on a blood panel is hyperglycemia. An elevated alkaline phosphatase occurs in only a minority of cases. Oftentimes the elevated alkaline phosphatase is due to liver changes from unregulated diabetes mellitus.
The urine cortisol:creatine ratio test is helpful in cats, especially since it is a relatively stress free test compared to blood sampling. If the test is normal then there is much less of a chance that Cushing’s is present. It the test is elevated it might be Cushing’s, but there are also other situations that cause this elevation.
The ACTH stimulation test is used, but two blood samples need to be analyzed at 30 and 60 minutes, instead of the 1 sample at 2 hours for the dog. This is because the increase in cortisol is variable in the cat. False negatives are common. False positives occur in stressed cats or those with non adrenal illness.
The LDDS test is used but the dexamethasone that is injected needs to be given at a higher dose. This test, when used in conjunction with the ACTH stimulation test, is one of the best ways to diagnose Cushing’s in the cat.
The HDDS test to differentiate PD from AT has not been refined to the point that is of diagnostic value.
In general, results of these tests can be variable, and must be interpreted in conjunction with the history and clinical findings. In light of the fact that Cushing’s is uncommon in cats, these tests need careful interpretation.
If the above tests suggest Cushing’s then radiology can be helpful since up to 30% of feline adrenal tumors are mineralized. Other radiographic findings include hepatomegaly and obesity. Ultrasonic evidence of an enlarged adrenal gland (especially if unilateral) or changes in internal adrenal architecture is strong evidence of an adrenal tumor (AT).
Adrenal tumors occur in about 20% of feline Cushing’s. They can be malignant or benign.
Medical therapy is generally unrewarding. Ketaconazole can be used, but the effects are variable, and side effects can occur. Mitotane might help, along with metyrapone. Metyrapone may be more helpful as a presurgical stabilization prior to surgery. Anipryl has not been used in cats.
Surgery is needed to remove one of the adrenal glands if the gland has a tumor, and both glands if the problem is PD. If both glands are removed the cat has to be on supplemental cortisone and mineralcorticoids for the rest of its life. Some cats with concurrent diabetes mellitus will no longer have the disease when their adrenal tumor is removed.
Unfortunately, cats with Cushing’s can be poor anesthetic risks due to diabetes mellitus and fragile skin. When this occurs we sometimes will use medical therapy to help control the problem and make our patient a better anesthetic risk.
The most common hormone problem encountered in dogs is hypothyroidism. It results when the thyroid gland does not secrete an adequate quantity of thyroid hormone called thyroxine. Many internal organs are affected, and the resulting problem depends on which organs are most affected.
Cats do not get this problem, but get an opposite problem called hyperthyroidism. Their problem involves excess thyroxine and its effect on the internal organs.
The thyroid gland is a small gland located at the throat, near what might be termed in people the “adam’s apple”. It has two lobes, and can be felt with careful palpation.
In this view of the thyroid gland you can also see the parathyroid gland at the far left and the lymph node underneath.
The role of the thyroid gland is to take iodine and convert it into the 2 main thyroid hormones; thyroxine (T4) and triiodothyronine (T3). T4 and T3 then circulate through the bloodstream and affect the metabolism of every cell in the body.
To control the level of these hormones the hypothalamus and pituitary secrete compounds called releasing factors. In the case of the thyroid gland, they secrete a releasing factor called thyroid stimulating hormone (TSH). It is the amount of TSH circulating in the blood stream that tells the thyroid gland how much thyroxine to secrete. In a very refined feedback mechanism between the hypothalamus, pituitary, and thyroid gland, the cells of the body get just the right amount of T4 and T3.
Thyroxine circulates throughout the bloodstream and affects almost all organs. It plays a major role in controlling metabolism, and is needed for growth.
Primary hypothyroidism accounts for almost every case. It has 2 main causes:
This cause, also known as autoimmune thyroiditis, occurs when the body makes antibodies against the thyroid gland. This effectively destroys part of it, so it has less thyroxine to secrete into the bloodstream. It is one of the most common causes of primary hypothyroidism.
This cause of hypothyroidism can start early in life. Symptoms will appear when it progresses to the point that the reserve power of the thyroid gland is affected.
In this form we do not know the cause, which is why it is called idiopathic.
Secondary hypothyroidism accounts for only a small percentage of cases. It arises when there is a lack of TSH, or secondary to some medications or diseases.
There are other causes of hypothyroidism that are encountered only rarely.
Thyroxine affects many internal organs, so a deficiency can have various symptoms. Classic symptoms include mental dullness, lethargy, obesity, and heat seeking behavior, although many hypothyroid dogs do not have any of these symptoms.
Early diagnosis of hypothyroidism is beneficial because a dog can have this disease and not show any symptoms for many years. In every disease we treat, the sooner we start the better-this applies particularly to hypothyroidism.
This is the most common manifestation of hypothyroidism. Typical skin symptoms include symmetrical hair loss (alopecia) along the trunk, although the hair loss is not consistently symmetrical. The hair coat is thin and dull, the hair easily falls out, it grows back slowly, and shedding occurs more often. Sometimes the hair coat resembles that of a puppy. Alopecia, if it occurs, is more common at pressure points and the tail.
The skin might be cool to the touch and be darker (hyperpigmentation) than normal. A leathery feel called lichenification might also exist. Hyperpigmentation and lichenification usually occur when the problem has been long-standing. Also, the skin might be greasy due to seborrhea, and inflamed due to secondary bacterial or fungal infections. These secondary complications might cause excess scratching (pruritis) and odor.
They skin lesions present in hypothyroidism mimic those in other skin conditions, especially allergies.
This terrier has hyperpigmentation on its neck. Hypothyroidism is not the only potential cause of this condition.
The ears can be affected, resulting in hair loss, inflammation and infections.
Neurologic signs might be seen, and include dullness, mood swings, muscle wasting on the head, facial paralysis, head tilt, disorientation, muscle weakness or paralysis, and lameness. On very rare occasions there will be seizures, and coma. Two specific diseases associated with hypothyroidism are megaesophagus and laryngeal paralysis. A loss of smell and taste are also possible.
This is a severe head tilt in a cat. There are numerous other causes to head tilt, most of them are more likely than hypothyroidism.
The cornea might undergo fat (lipid) deposits or become ulcerated. Changes with adequate tear production along with internal structures of the eye could occur.
When a dog does not produce enough tears to keep the cornea moist it develops a disease called keratitis sicca. A tenacious discharge adheres to the eye and makes it susceptible to many problems.
Diarrhea, constipation and vomiting, if they occur, could occur in hypothyroid dogs.
Abnormalities in heart strength, rate and rhythm, along with atherosclerosis, could occur.
Arrhythmia’s are usually diagnosed with an electrocardiogram (ECG). This is a lead II ECG on a pet with a heart rate of 106 beats per minute.
Inadequate thyroxine makes the immune system less effective at fighting infections, especially the bacterial skin infections (pyoderma) that occur secondarily. Suppression of the immune system might even increase susceptibility to demodex.
Anemia is the most noted symptom. anemia is not a disease but a sign of disease. It occurs when the red blood cells are low. There might also be a bleeding tendency, low white blood cells from bone marrow suppression, and low platelets.
This blood sample shows three different tests on a CBC that check for anemia.
RBC- red blood cell count
HGB- Hemoglobin level
Breeding dogs might have abnormal heat cycles, infertility, and high puppy mortality. Testicular atrophy and low sperm, or no sperm.
In addition to low thyroxine, hypothyroidism is implicated in sugar diabetes (diabetes mellitus) and addison’s disease (hypoadrenocorticism).
Thyroxine is essential for the development of bones in young animals.
The arrow point to growth plates, areas of bone growth that allow the bones to grow longer. The top arrow points to the end of the thigh (femur) bone, the bottom arrow points to the beginning of the shin (tibia) bone.
Due to the vast number of organs influenced by thyroxine, and the fact that many skin conditions have similar symptoms, numerous diseases have to be kept in mind when making a diagnosis. These include Cushing’s disease, skin allergies, sarcoptic mange, demodectic mange, and Ringworm.
A thorough approach is needed for a correct diagnosis of hypothyroidism. In every disease we encounter we follow the tenet’s of the diagnostic approach to ensure that we make an accurate diagnosis and that we do not overlook some of the diseases that are also encountered in pets as they age.
Hypothyroidism can occur at any age, although it tends to be a problem that affects middle aged and older dogs, especially the larger breeds.
Several canine breeds are prone to getting hypothyroidism:
Females and males get it at about the same frequency, neutered pets might be at higher risk of hypothyroidism
Hypothyroidism disease is suspected in any pet that has some of the symptoms described above, particularly the skin symptoms. It is important to remember that some dogs do not show any symptoms early in the course of the disease. This is another reason for yearly exams and blood sample with thyroid test in dogs and cats 8 years of age or more.
Other findings include skin infections that recur after antibiotic therapy is stopped.
Routine physical exam findings might include:
There is no one test that definitively diagnoses hypothyroidism, save for a thyroid biopsy.
A CBC (complete blood cell) and biochemistry panel should be run on every dog 8 years of age or more, especially if they have any of the symptoms of hypothyroidism.
The CBC might show anemia or an elevated WBC (white blood cell count). The anemia is due to thyroxine’s direct effect on red blood cell production, the elevated white blood cell count (leukocytosis) is due to secondary bacterial infection.
The biochemistry panel might show an elevated cholesterol. Diet can influence this test, along with how long after a meal was the blood sample for this test obtained. To be accurate there should be a 12 hour fast when assessing cholesterol levels.
Liver tests might also be elevated, presumably from fatty changes that occur in the liver due to abnormal metabolism.
The biochemistry panel is very comprehensive. This high cholesterol alerts us to keep hypothyroidism in our tentative diagnosis list. Notice the elevated amylase and lipase tests above the cholesterol test? These are indicative of pancreatitis, which is exactly what this dog has.
Many factors affect the level of thyroxine that circulates in the bloodstream, including normal fluctuations. As a result, there is no blood sample that definitively makes a diagnosis of hypothyroidism. Over the years many different test have been developed to help us detect adequate levels of thyroxine in the bloodstream. Our goal is to diagnose those cases where the problem is not so obvious, and also not to over diagnose this condition.
Our routine blood sample has an add on test called a T4 test. If this test is normal, everything else being equal, a dog probably does not have hypothyroidism.
This routine thyroid test by RIa (radioimmunoassay) is at the high end of normal. This dog most assuredly does not have hypothyroidism.
If the thyroid test is low or low normal, then 2 main scenarios are possible:
The first scenario is called the sick thyroid syndrome or nonthyroidal illness (NTI). In this situation the thyroid gland is normal, but there are factors that are suppressing it from secreting a normal amount of thyroxine into the bloodstream. These factors include medications like cortisone, valium, anticonvulsants, and sulfa antimicrobials. Diseases like Cushing’s disease, diabetes mellitus, chronic renal failure, liver disease, and addison’s disease can also cause NTI. When these factors are corrected, or these diseases are treated, the apparent hypothyroid problem corrects itself. No treatment with supplemental thyroxine is needed.
In the second scenario the thyroid gland is having a problem secreting adequate thyroxine due to one of the causes previously mentioned in the causes section. This is the hypothyroidism we need to treat with supplemental thyroxine.
How do we differentiate between a true hypothyroidism from the sick thyroid syndrome. We have another blood sample that aids us, called the free T4 test by equilibrium dialysis. If this is low, and the signalment, history, and physical exam are consistent with this disease, then a diagnosis of hypothyroidism is made.
This dogs T4 level by equilibrium dialysis is low, so it most likely has hypothyroidism
Biopsies of the skin can show changes associated with hypothyroidism. These changes can also occur with other skin conditions though, especially those involving the endocrine system.
The comments section of this skin biopsy report mentions endocrinopathies (hormone diseases like hypothyroidism) and corticosteroids (cortisone) as possible additional causes of this dogs skin problem.
This is the most reliable test to confirm a diagnosis of hypothyroidism. It eliminates some of the variables that suppress thyroxine production by the thyroid gland. Unfortunately, it is difficult to find TSH of animal origin. Human recombinant TSH is a possible replacement, but cost might preclude its use.
An actual biopsy of the thyroid gland can be taken. This test is rarely utilized since there are many other good tests that are not so invasive.
Radioactive Iodine can be used to outline the thyroid. We tend to use this test much more often in feline hyperthyroidism
One of the tenets of the diagnostic process is whether or not a treatment that is instituted actually corrects the problem. This might apply in hypothyroidism, but it might not. In some situations we have no choice but to try supplementation. We reserve this for cases when the thyroid tests are suspicious (normal but at the low end of the normal range), we find no evidence of other disease processes, and the dog has symptoms consistent with hypothyroidism.
This approach has disadvantages though. Since thyroxine affects metabolism, an increase in metabolic rate due to supplemental thyroxine might correct some of the symptoms encountered, even increasing hair growth. This does not necessarily mean that these symptoms that were consistent with hypothyroidism were actually caused by hypothyroidism. A delay in the correct diagnosis leads to a delay in proper therapy and a worsening prognosis.
When hypothyroidism is correctly diagnosed, the treatment, called levothyroxine (T4), is continued for life. Levothyroxine has various trade names, including Soloxine and Synthroid.
This is the brand we use. It is best to stay away from generic levothyroxine because it is not absorbed as well as the name brand version.
Medication is given every 12 hours. A thyroid level needs to be checked initially at 1 month to make minor adjustments. The thyroid pill should be give 4-6 hours prior to the recheck blood test. It is then checked every 6 months in order to refine the dose, because the body does change in the amount of thyroxine released by the thyroid gland. Also, as pets age, their cells vary in their need for thyroxine.
In the first week of treatment many dogs will be more alert and more active. Within one month improvement in problems related to metabolic changes will be noted, and within 2 months most skin conditions will be improved. If there is no response to therapy within 3 months, and the proper dose and type of levothyroxine are being used, then further diagnostic tests are needed to look for other diseases. It might take 6 months or more for all changes to return to normal.
It is possible to overdose your dog with levothyroxine. Symptoms include excess drinking and urinating, restlessness, and increased appetite. If you suspect this is occurring stop medicating and bring your dog in for an exam. Checking the thyroid level every 6 months will help eliminate this problem.
Pets that have heart disease, diabetes mellitus, or Cushing’s Disease(hypoadrenocorticism), may need altered doses of medicine if they occur concurrently with hypothyroidism. The dose of levothyroxine in these pets, if used at all, needs to be conservative to prevent other problems.
An additional treatment modality is called VNA. It is a non-invasive and non-painful way to stimulate the nervous system to help the thyroid gland heal on its own.
Since this disease has a strong genetic component selective breeding can help minimize occurrence. Screening for anti thyroid antibodies in breeding animals can be utilized once they have reached puberty. These antibody tests are sent to special labs at Michigan State University or Cornell University.
The use of VNA can have substantial positive effects in this disease.
A very frustrating skin disease found mostly in dogs is called acral lick dermatitis (ALD), commonly know as a lick granuloma. Dogs with this disease lick incessantly, causing chronic skin lesions of the limbs.
Many aspects of ALD are similar to allergic dermatitis in general. This page will give you an opportunity to link to the aspects of the allergic dermatitis page that also apply to ALD.
Constant licking leads to hair loss and irritation of the skin. As the problem progresses the skin becomes ulcerated and infected. As the ulceration progresses nerves become inflamed and the area becomes pruritic (itchy), so much so that the dog can not stop licking. A vicious cycle develops and the condition becomes chronic.
It is theorized that some dogs get into such a licking habit, and actually derive pleasure from it, that once the initiating cause is eliminated they still continue to lick.
This is a disease that has many factors involved with the cause. Some of these work in combination, adding to the complexity of the problem. In some breeds, notably Doberman Pinschers and Great Danes, the cause might not be found. The most common causes include:
This is considered the primary cause of the problem. We have a detailed page on allergies to learn more about this complex problem. Food allergy is a component of this also.
Joints in the area of the lesion can be painful, causing excessive licking of the skin over the area. Since the licking does not cure the problem, it continues, eventually causing significant skin lesions.
Inflammation of the nerves under the skin in the area of the lesion can cause significant discomfort, again leading to excess licking.
Skin cancer can cause chronic lesions that are uncomfortable and lead to chronic licking.
Deep seated fungal infections, including blastomycoses and Ringworm can initiate the problem.
This is a catch-all term for psychological causes that are thought to be involved. They include boredom and stress factors. Similarities have been made between this and obsessive-compulsive disorders in people. When you see a dog licking incessantly at his legs you can see why this comparison is made.
The most consistent symptom in pets with ALD is excessive licking of the extremities, especially the front and rear legs. Lameness could occur due to infected skin or even arthritis. If the skin infection is serious enough there might be a lack of appetite (anorexia) or lethargy.
The correct diagnosis for ALD does not come easy, so a thorough approach is needed. In every disease we encounter we follow the tenet’s of the diagnostic process to ensure that we make an accurate diagnosis, and that we do not overlook some of the diseases that are also encountered in pets as they age.
Several breeds are prone to ALD:
ALD usually starts appearing when dogs reach at least 5 years of age, especially the above breeds. When it first appears it might coincide with allergy symptoms that are seasonal in nature.
This is a picture of the classic finding in a dog with ALD.
If the skin infection is severe enough there might be swelling (cellulitis) due to the infection. Also, the lymph node that drains the affected area might be enlarged and there might even be a fever.
Diagnostic tests are important since many skin conditions look the same, even though they have different causes and are treated differently. In some situations other skin diseases can occur simultaneously with ALD.
Ringworm lesions can look similar to ALD lesions. In Ringworm there is usually not as much licking.
If we suspect the licking is from a painful joint we can sometimes make this diagnosis from an x-ray.
This test is used to help differentiate skin tumors or deep fungal infections as the initial cause of ALD.
As an alternative to an actual skin biopsy we can do a simpler test called a fine needle aspirate. In this test we use a syringe with a tiny needle to take a sample of the affected area. This sample is put on a microscope slide for analysis by one of our pathologists.
It does not require general or local anesthesia and can be performed during an office call. Only a small amount of tissue is sent to the lab for analysis, so it is not always possible to make a complete diagnosis this way.
This test will give us an indication of the type of bacteria involved. Staphylococcus and Enterobacter are the more common pathogens. Since the top of the lesion is contaminated with many bacteria, some of which are not part of the problem, a culture is performed on biopsy samples that are taken in a sterile manner.
Allergies can be a major component of ALD. Please refer to our allergic dermatitis page due learn about allergy testing.
ALD tends to be a chronic disease that leads to significant frustration. The wide variety of treatments that are used to treat ALD are an indication of the complexity of this disease and the fact that many different causes, some working in tandem, are involved.
We can not emphasize the importance of proper flea control in any pet that has a skin condition since we live in a flea endemic area year round. Even pets that are 100% indoors are possible flea victims.
The products available today are a significant improvement over flea control products in the recent past. They are economical, safe, effective, and very convenient. The two main products we recommend are Trifexis for dogs© and Revolution for cats©. We have detailed brochures on each to explain how they work, please ask one of our receptionists. In addition to treating fleas they prevent heartworms and treat parasites.
Cortisone is used initially to minimize swelling and licking. It is not used as the primary means to control ALD in the long term since a skin infection is almost always present and cortisone decreases the immune system’s ability to fight this infection. Cortisone is used much more often in treating allergic dermatitis. There is a section there on its proper use.
As an option to using cortisone to minimize the licking we suggest the use of elizabethan collars. A good option that is tolerated well by larger dogs is a small plastic bucket with a hole cut out of the bottom that is placed over the head.
Oral antibiotics are the most important treatment we have for ALD. In some cases we need to use them for 4-6 months due to the chronic nature of the problem. It is important to continue them for at least 3 weeks after the skin looks healed. In some pets we put them on intermittent antibiotic therapy for the rest of their lives- this is called pulse therapy.
Antibiotics that work best include:
We have had success using our laser machine in the treatment of this problem. It usually takes at least 3 treatments, and in some cases can be a significant help in minimizing the licking.
This Labrador has an ALD lesion on top of its rear foot area. It is been prepped or laser treatment.
The laser is being used at a light setting with an intermittent pulse.
The appearance of the lesion immediately post laser treatment.
Initially it is useful to put your pet on pain medication until the antibiotics and other treatments start working. NSAID’s like Rimadyl can because because they decrease inflammation and also pain. Tramadol can also be used initially.
If a deep seated fungal infection is diagnosed we will use oral fungal medication for an extended period.
This can be a good way to minimize itching without using cortisone. The less we use cortisone to minimize itching the faster the problem will resolve. These are injections give on a long term basis, usually once per month once the allergy is improving.
We recommend feeding hypoallergenic diets to any pet that has a skin condition caused by an allergy.
Some allergic dogs and cats scratch less when supplemented with essential fatty acids. The main ones we use are Derm Caps and EFa-Z.
This is not a rewarding way to treat ALD since the problem commonly recurs after the surgery.
It is a natural tendency to want to use topical medication only on a skin problem. If used in combination with long term oral antibiotics this topical medication can be beneficial. They are not effective when used alone.
Some dogs are compulsive lickers without any obvious cause. Some veterinarians believe that the incessant licking in ALD is similar to the exaggerated grooming habits of people with obsessive-compulsive disorders.
These medications are helpful, but do have the potential to cause side effects, especially when used with other medications. One of our doctors will let you know if they apply in your situation.
An additional treatment modality used to treat ALD is VNA. It is a non-invasive and non-painful way to stimulate the nervous system to stop the sensation that is causing the problem.
ALD has a guarded prognosis. An early and accurate diagnosis (when one is apparent) offers the best option by instituting proper medication before the problem becomes so chronic that treatment is only marginally effective.
An occasional cause of skin conditions in pets is caused by Ringworm. The scientific name for this disease is Dermatophytosis. It is caused by a fungus not a worm, and the lesion is not always in the shape of a ring. Since fungi are everywhere in our environment, it is difficult to determine which pets will develop the problem. The fungus that causes Ringworm can be cultured from the hair coats of normal dogs and cats. These pets might be carriers of the disease to other pets along with people. We tend to see the problem more in young animals.
People will sometimes pick up a case of Ringworm from their pet, but just because a pet has Ringworm does not necessarily mean that the people that interact with that pet will develop the problem. A dog or cat can transmit Ringworm to a person without showing any symptoms at all.
There are 3 specific fungi of significance in this disease.
The source of this species of Ringworm is almost always a cat.
This species of Ringworm is usually from dogs and cats that dig into contaminated soil.
This species infects dogs and cats when they are exposed to rodents or the burrows they live in.
In cats, almost all cases of Ringworm are caused by Microsporum canis. In dogs the majority of cases are caused by Microsporum canis. Which of these 3 main dermatophytes causes the Ringworm in dogs depends on geographic location.
The skin lesions that appear with Ringworm are variable, and do not necessarily form a ring. There will be hair loss, usually in small patches at first. as time goes on the patches may disappear or appear at other locations on the skin. There might be scratching due to itchiness. If the hair loss occurs on the face or feet there is a chance it is due to digging habits or exposure to rodents.
This patch is typical of the lesion seen in Ringworm. A diagnosis of this disease can not be made based just on the appearance of this lesion because other skin conditions (Demodex for example) can show similar lesions.
There are several different ways to diagnose Ringworm. All require some type of test because it is impossible to make the diagnosis just by looking at the skin. This concept holds true for all skin conditions; making a diagnosis of a skin disease requires all of the aspects of the diagnostic process.
If a person in a household has been positively identified with Ringworm by their physician it is possible they obtained it from their pet, even if their pet has no symptoms of the disease. This is especially important in multiple cat households. We will culture these pets using the culture technique we describe below, but in this case, we might run a new toothbrush over the hair coat to obtain a sample for culture.
One of the simplest ways to diagnose Ringworm is with the Woods lamp, which is an ultraviolet lamp, also know as a black light. 50% of the Microsporum canis species will fluoresce when the Woods lamp is placed near the area of hair loss.
The lamp emits a purple/blue glow from the tube, and when there is fluorescence on the skin, it has a greenish appearance. Other material on the skin (dander, medication, etc.) can also fluoresce, so interpretation is important.
Since only 50% of a certain species of Ringworm fluoresces under the glow of the Woods lamp, a culture is used to verify the diagnosis:
The first step in the culture process is to gently remove hair follicles in the area of the lesion
These hairs are cultured in a special media that inhibits bacterial growth and enhances fungal growth. This culture can be sent to our outside lab or done in house. Since a fungus is a slow growing organism it can take up to several weeks to determine if there is growth or not.
The positive culture on the right, from our in house lab, demonstrates two findings that are needed for a positive diagnosis. The first is the cottonish fungal growth, and the second is the reddish color of the culture media. This color change must occur at the same time the fungal growth appears.
|The culture media prior to the start of the test.||Positive fungal growth after 10 days of incubation at room temperature.|
Topical shampoo therapy is used in almost every case, especially in longer haired pets. It is common to clip some or all of the hair in some pets to make it more effective. These baths will also remove infected hairs that can be the source of an infection to people or other animals.
Specific anti fungal cremes are also used when a pet is infected in an area that already has sparse hair growth, or there are small, discrete lesions.
Oral anti fungal medications are also used in select cases. They have the potential to cause side effects, so their use is confined to specific situations.
In some pets the disease may resolve by itself.
Since fungi are everywhere it is almost impossible to prevent exposure. Pets that chase rodents, especially into burrows, might be at an increased risk.
Allergies are a common cause of skin conditions in dogs and cats. This type of allergy goes by several names: the most common are atopy, allergic skin disease, or allergic inhalant dermatitis.
The main difference between us and pets is that allergies in pets tend to cause skin conditions, as opposed to runny eyes, runny noses, and sneezing we encounter in people. Along with other skin conditions besides allergies, symptoms typically include scratching and itching. Medically this is called pruritus.
Allergies can be hard to control and are chronic in nature. This causes significant frustration for pet owners and discomfort for pets. A correct diagnosis along with proper therapy instituted early in the course of the disease will minimize this frustration. Many pets stores and groomers will give advice on a “food” to feed to cure your pet’s skin condition. It is irresponsible for them to be giving any advice of this nature due to the numerous causes of skin conditions, let alone the complexity of this disease, and also the fact they have not examined your pet and do not have any important physical information about your pet. We have a short page on Nutrition Advice that addresses this issue of people giving medical advice when they have no business doing so.
This page summarizes and generalizes the complex problem know as allergic skin disease. It is detailed, and will take a few minutes of your undivided attention to help in understanding this problem.
In the beginning of this page we will give you the background of their causes and how we diagnosis them. We will take about treatment towards the end.
When the immune system encounters an allergen that has the potential to cause disease (ex. parvo virus) it produces antibodies called IgG (immunoglobulin G, previously known as gammaglobulin) and IgM (immunoglobulin M). For the first 7-14 days of infection the virus spreads throughout the body because not enough antibodies are produced to stop them. Within 7-14 days enough antibodies are made to neutralize the virus, and the pet eventually recovers from the disease, all other things being equal.
As time goes on, the now sensitized immune system is ready to produce large amounts of antibodies rapidly the next time it encounters this virus. The rapid antibody response neutralizes the virus immediately, instead of taking the 7-14 days that occurs the first time it encountered the virus. This is called the anamnestic response, and is why a pet that recovers from parvo virus does not get the disease again.
A different scenario presents itself when the immune system encounters an allergen that is not necessarily pathogenic (ex.- a pollen particle). A different part of the immune system kicks into high gear when these non pathogenic allergens invade the body.
When a pollen particle enters the body for the first time (through the skin or respiratory passage) it stimulates the body to produce antibodies also, this time they are called IgE (immunoglobulin E). This IgE antibody attaches to the allergen in order to neutralize it, just like IgG would do to a parvo virus. This process, called sensitization, occurs in the first season a pet encounters a specific allergen in its area. Without this sensitization there is no allergy. This type of allergy is the most common type, and is called atopy or atopic dermatitis.
The next time a pet encounters these pollen particles (usually the next allergy season), the immune system produces large amounts of IgE antibodies rapidly because it has been sensitized to them from the previous season. Again, this is similar to what happens when the immune system makes IgG and IgM antibodies against parvo virus.
IgE, with attached allergens, circulates throughout the bloodstream to a type of cell called the mast cell. Mast cells contain many chemicals that can cause inflammation, the most important of which, in relation to allergies, is called histamine. When an IgE antibody (even IgG can be involved) with an attached allergen encounters a mast cell under the skin, it alters the membrane of the cell, and histamine leaks into the surrounding tissue. Histamine causes inflammation, noted as redness (erythema) and itching (pruritus) on the skin surface. The reaction that is seen on the skin surface is called a wheal or a hive. This causes your pet to lick, scratch, or bite at this area which now itches.
It is the mast cell, that releases histamine when it encounters an IgE antibody with a pollen particle attached, that is a major component of allergies. This is what occurs in atopy and is suspected to occur in food allergy. In flea allergies, it is an allergic reaction to the flea saliva that causes the immune system reaction.
Other immune mediators are impliacated in atopy. They include cytokines, neuropeptides, peptides, proteases, and leukotrienes. They can affect nerve fibers to the skin, causing itchiness.
As if that is not enough, there are other immune mediators called Interleukin 31 (IL-31) that are involved. It’s an understatement to say that the immune system is very complicated. Add the ever present skin bacteria to this equation and it is easy to see how this can become a frustrating problem.
Food allergies have a slightly different pathophysiolgy then atopy in some cases. In food allergies, the offending allergen (usually a protein) is absorbed through the lining of the small intestines and proceeds right into the bloodstream. This causes a different immune system reaction. If the intestines are inflamed from some other disease process, for example IBD (inflammatory bowel disease) in cats, the normal barrier lining the intestines is compromised and more allergens can enter the bloodstream.
There are 3 main types of allergies in relation to skin conditions. It is possible for a pet to have a combination of all 3 allergy types:
The least common cause of skin allergies is food allergy, although pets stores and groomers are under the impression that this is the sole and most important cause of skin allergy, which is why they give amateur advice on what to feed. They are in the business of selling food, which is why they only see food as a solution to atopy, when it is the least common cause. Our page on Nutrition Advice has much more information on this topic.
It is important to distinguish food intolerance from an actual food allergy. They are not the same, but many people giving amateur advice on this problem do not understand the difference.
In the vast majority of cases, food allergies are caused by an allergic reaction to proteins in food. The size of the protein particle is important. They have a molecular weight of between 18 and 70 kilidaltons (kD). In laymens terms, they are very, very tiny.
Heredity is a major predisposing factor in people, and probably so in animals.
Some of the more common food allergens in dogs and cats are:
|dairy products||rawhide chews and dog biscuits/treats|
In dogs, beef, dairy products, and wheat tend to cause most of the problems, with chicken, lamb, and soy following. In cats, beef, dairy products, and fish account for most of the food allergies. Premium dogs foods can contain these products, so just because you are feeding a higher quality or more expensive food doesn’t mean that food will not cause a food allergy.
Many pet stores are there to sell food, so they will tell you a certain type or brand of food will cure your pets skin (and other) conditions. The employees of these stores have no business giving their advice unless they are licensed nutritionists for animals, or are licensed veterinarians, and have discussed with you the following points that are so important in making a diagnosis of any disease, including allergic dermatitis:
Most of the symptoms of food allergy involve inflammation and scratching of skin or ears, but might also include vomiting or diarrhea. These gastrointestinal symptoms tend to occur more in cats.
In those pets that truly have food allergy, a high percentage also have atopy at the same time. Cats might have more food allergies than dogs, although fleas are a common cause of skin allergy in cats.
The most consistent symptom in pets with allergic skin disease is excessive itching. The medical term for this is pruritus. High strung dogs might itch more than placid dogs. Chewing, biting, or licking, or rubbing the skin can all be manifestations of pruritus.
Dogs can chew so incessantly that they wear down their incisor teeth to the gumline
In dogs some of the more common areas for pruritus to occur are the face, feet, and armpit areas. As the problem progresses the whole body might be involved. Some pets will scratch excessively but not show any problems with their skin.
If your pet has an allergy to fleas you might find tiny blood spots where it has layed down. These are the result of flea dirt that has fallen off your pet and become wet. Since flea dirt is made up mostly of blood that the flea has sucked out of your pet and has passed through its digestive tract, they appear as small blood spots on the floor or table tops when wet.
The slight redness (erythema) to the face of this dog.
The dark, stained areas on this poodle’s foot are due to excessive licking. The color change is due to the chronic saliva on the hair, and the changes it causes on the hair coat.
This dog’s skin is oily from chronic rubbing. This loss of hair is called alopecia.
This Golden Retriever has significant redness (erythema) on its ear flaps. Chronic ear inflammation or infections can be a sign of atopy or a food allergy.
The above pictures were all caused by atopy. They could have been caused by other diseases though, so you cannot make a diagnosis of a skin condition just by looking at them.
Cats get skin allergies also, although not as frequent as in dogs. They might exhibit the same or different symptoms. Different symptoms include tiny bumps throughout the body, ulcers on the lips, excoriation of the neck, and even patches of missing hair (alopecia) without any skin lesions. Ear problems related to allergies are rare in cats compared to dogs. Cats get a problem called psychogenic alopecia that can be similar in appearance to atopy.
It can be difficult to tell pruritus from normal feline grooming. Vomiting hair balls, hair in feces, and hair in your cat’s mouth when you brush its teeth (you are doing this aren’t you?) are all clues.
This cat has an allergy that caused it to irritate the skin above its eye by rubbing its face
This is a severe version of an ulcer on the lips. It is called the Eosinophilic Granuloma Complex.
Since the symptoms of allergic skin disease mimic those of other skin diseases, a thorough approach is needed to differentiate them. In every disease we encounter we follow the tenets of the “diagnostic process” to ensure that we make an accurate diagnosis, and that we do not overlook some of the diseases that are also encountered in conjunction with skin diseases.
It is too easy to jump to the conclusion as to what is causing your pet’s pruritus. Here is a list of possible causes of scratching and itching in pets in random order:
|Lhasa apso||Miniature schnauzer|
This dog has licked so much it has maimed itself, and now has pyoderma, which is a skin infection, typically a Staph. infection
This is an inflammation of the eyes. The green discharge in the corner of the eye is from fluorescein stain that was checking for a scratch on the cornea.
Chronic licking and scratching can cause thickening and dark pigmentation of the skin. The white arrow points to mild hair loss, hyperpigmentation, and lichenification in a Yorkie.
Commonly know as a hot spot, it is an area of skin that has been maimed from intense pruritus. Pyoderma is also present, and the skin is very painful. Hot spots occur rapidly and can encompass a large section of skin in a short time. Affected areas usually include the rump and the side of the face. Other common causes of hot spots include anal gland problems, ectoparasites like mange, grooming, and deep skin infections. Golden and Labrador retrievers, St. Bernards, Collies, and German shepherds are more prone than other breeds.
The serum that is exuded from the inflamed skin matts the hair and causes the problem to progress under the hair coat without anyone realizing how serious it is. These pets can be so painful that we need to sedate them prior to clipping the hair and cleaning the wound.
Hot spots can progress and cause serious skin conditions. What looks like a minor skin wound with matted hair can actually be a serious and painful infection once the hair is removed.
This is an infection of the outer ear canal. Sometimes this is the only symptom of allergy, especially food allergies. This ear is so severely infected that it is difficult to ascertain the normal anatomy. The ear canal is completely occluded, necessitating surgery to correct it. This dog is painful.
Infection of the feet can occur from chronic licking.
These are commonly known as lick granulomas. There are many causes, allergies being a primary one. Other causes include arthritis, skin tumors, inflamed nerves, fungal infections, ectoparasites, and psychological factors like boredom and stress. Once the licking starts the problem is difficult to control. In some cases we have found that the use of the laser has been a significant help. The most effective treatment is the use of antibiotics for many months.
This small lick granuloma is on the front leg of a Golden Retriever
Flea dirt is literally droppings from the flea after is has bitten a pet and the blood has passed through the flea’s digestive tract. It looks like pepper, and is easily visualized on a pet with a white hair coat.
This is an example of lots of flea dirt.
Flea eggs are small white particles, similar in size to flea dirt, that fleas lay in a pet’s hair coat. They eventually drop off and contaminate the environment. A pet can have fleas, yet show no evidence of fleas, flea dirt, or flea eggs.
Flea allergy dermatitis typically does not cause hair loss around the face, eyes, and ears like in atopy, although this is not a hard and fast rule.
It is important to do a skin scraping in many cases of allergy because the lesions of atopy commonly mimic those of other diseases. Ectoparasites like demodex or scabies can cause skin lesions and itching.
Ringworm can mimic allergy symptoms. Lesions from Ringworm tend not to be as pruritic as allergies.
Malassezia, another fungus, is commonly associated as a secondary problem when the skin is infected. Even though it is a normal part of an animals hair coat, it will add to the itching if other conditions are present. Common areas for Malassezia include the ears, lips, muzzle, between the toes, and the anal area. Indications that Malassezia is present include pruritus, erythema, and greasy skin with an offensive odor. These symptoms can occur with other diseases besides Malassezia.
Malassezia is diagnosed by the above symptoms and by looking for the organism under the microscope after swabbing the skin and placing the discharge on a microscope slide. Many pets respond to shampooing with specific antifungal shampoos twice weekly. These topicals will only work when the underlying allergy and its associated skin infection are under control. In some cases we use oral antifungal medications to control the problem.
Hypothyroidism can cause skin conditions, although dogs with only hypothyroidism are not terribly pruritic.
Hypersensitivity to internal parasites can cause symptoms similar to atopy. This is not a common situation.
In some cases it is difficult to make a diagnosis. When we are presented with this situation we will biopsy several small pieces of infected skin and have them analyzed by a veterinarian that specializes in tissue analysis of the skin.
Here is a typical report from one of them. All of the big words mean that in this skin biopsy an allergy is most likely, but autoimmune disease cannot be ruled out for sure.
Allergy tests are performed in cases where we already have a diagnosis of allergy. The main purpose of allergy testing is to find exactly what your pet is allergic to, and also to set up a protocol for allergy injections. If giving allergy shots is not contemplated then this test is of less value, although it will let us know what allergens we want to avoid. Trying to avoid these allergens though is the hard part because they are in our houses and almost everywhere outside.
There are two main types of allergy tests that are performed. Neither one is perfect, and they can have false positives and false negatives. They are not accurate in diagnosis a food allergy.
Most of us are familiar with the first one. In this test, called the allergy skin test or intradermal test, small amounts of materials that routinely cause allergies in dogs are injected under the skin. The reaction, if any, is graded, and a determination is made as to whether or not a pet is allergic to that specific allergen.
This test is very subjective, and therefore prone to errors in interpretation, and therefore requires significant experience. Many different techniques are used.
Your pet must be off of oral cortisone medication for at least 1 month before testing. If injectable cortisone is given, the waiting time is longer. Your pet must not be on any tranquilizers at the time of testing and must be off of any antihistamine medication for 10 days.
Pets usually are given a sedative to calm them and to minimize the release of cortisone due to stress, which will affect the outcome. The hair on the side is clipped where there is no current dermatitis occurring. A tiny amount of histamine is injected first. If there is no reaction to histamine, the full test is postponed. A small amount of sterile saline is also injected as a control.
The areas where the allergen is injected are marked
Numerous allergens are injected into the skin and a reaction is noted at 15 minutes and again at 30 minutes. The reaction we are looking for is called a wheal. A positive test to a specific allergen occurs when the reaction is in between the saline and histamine tests in size.
In some cases the wheal is obvious, in others it is subtle, which is part of the interpretation process.
The second type of test that is performed is called the RAST test. RAST stands for radioallergosorbent test. Another in vitro test is called the ELISA (enzyme linked immunosorbant assay) test. RAST tests for the levels of allergen specific IgE. In this test a blood sample is taken and submitted to a special lab for analysis.
The RAST test has advantages over the intradermal test. There is no clipping, sedating, and there is no potential to have an adverse reaction to an allergen injected into the skin. There is less of a chance that prior drug therapy (cortisone) will influence the outcome, and it can be used in patients that have dermatitis.
The primary disadvantage is the fact that false positives are more common when compared to the intradermal test.
The RAST test is very thorough and checks for many different allergens in the home, outside, and in your pet’s food. Here is an example of one of their reports:
Here are 4 of the dozen household allergens they tested. This dog is borderline for orris root and human epithelial cells, and positive for jute/sissal and tobacco smoke.
These are a few of the food allergens tested in this sample. There was no allergy to venison, eggs, or milk, but this dog was allergic to soybean. This give us a rough idea of what food your pet might be allergic to, and can only be confirmed with the trial elimination diet.
This is a tiny sample of the numerous allergens found in the environment tested for on the same dog as above.
Allergy tests can be unreliable at diagnosing food allergy. A better way to diagnose food allergies is using a technique called the elimination trial. By taking away a food that is suspected of causing the food allergy you can determine if the problem resolves. This might take up to several months to know for sure. To verify the diagnosis you need to feed the suspected food again to see if the skin condition returns. Commercial diets that contain rice, venison, fish, and potato are commonly used for the elimination trial. There is a food manufactured by Hills called Z/D that has been a big help in diagnosing and treating food allergies.
On occasion a specific type of white blood cell, called an eosinophil, is elevated in allergic conditions. Other conditions, notably worms, can also cause this elevation in eosinophils.
A routine blood panel can also give an indication of internal or hormonal problems that might show up as a skin condition. The most important of these are hypothyroidism and Cushing’s Disease.
This blood panel shows an elevated alkaline phosphatase level. This could be an indication of a hormonal problem called Cushing’s Disease.
In the early years of atopy the pruritus is more easily controlled. As the problem progresses treatment is not as rewarding. Chronic changes to the skin can occur, especially lichenification and hyperpigmentation.
Treatment is aimed at all the factors that contribute to pruritus. For example, a pet that is normally not atopic might become so if exposed to fleas, or if it gets a pyoderma, or is allergic to a protein in its diet. This concept is called summation of effects, and might push the pet over what is called the pruritic threshold. By minimizing one of these components you might keep your pet under the pruritic threshold and minimize its skin or GI symptoms.
Hypoallergenic means foods that your pet has never eaten, which technically, it cannot be allergic to. We recommend using these foods in some cases when we feel the pruritic threshold has been reached and any decrease in allergen load will put your put under this threshold. It might take up to 2 months to know if the food is working. You cannot feed any other foods or treats during this trial period, so plan on rewarding your pet with something else besides food.
There are 3 different diets to help:
Homemade diets can be beneficial, and have the advantage of controlling the protein and carbohydrates sources. It is important to pick a protein source your pet has never been exposed to. To be sure of this we sometimes need to resort to diets that contain some unusual ingredients.
Homemade diets have the substantial drawback of time, expense, guesswork, and being nutritionally incomplete. Some pets do not accept the food, and some of them develop diarrhea. For these reasons most pet owners do not use this treatment method.
Commercial Novel Protein Diets are a popular treatment for food allergies. Novel protein means your pet has never eaten this protein in the past. For them to work, just like homemade diets, the protein source has to be a food your pet has never been exposed to, which can be difficult to determine. Traditionally they have contained fish, lamb, potato, or venison. Many pets react to several different proteins compounded the problem. Compared to homemade diets commercial diets have the advantage of being nutritionally complete and convenient. It is becoming more and more difficult to find a food that conatins a protein that is truly novel.
In many cases these foods work well to eliminate or decrease the food allergy. It takes up to 8 weeks to know if they are working, and your pet needs to be fed only these foods and nothing else, and be off all medications to decrease scratching. You might have to try different foods to find one that works for your pet. Unfortunately, its possible for some pets to eventually develop and allergy to one of the novel proteins in the food you are feeding.
Commercial Hydrolyzed Protein diets are the best option in most cases. The advent of these diets for food allergies has been a big step in eliminating the problem. Instead of trying to find a novel protein, these foods have literally decreased the size of the protein particle that gets absorbed in the intestines into the bloodstream. This reduced size is now too small to cause a food allergy, no matter what the protein source initially. These foods are nutritionally complete, convenient, and the ones we tend to recommend in most cases of food allergy. The brand we use most is Hill’s z/d. Hill’s was the first manufacturer to identify this solution and z/d is still the gold standard. This food is unconditionally guaranteed and you will get your money back if you are not satisfied.
It is important that you do not have your pet on cortisone or antihistamines while trying to determine if your pet has a food allergy, since they will decrease the scratching and lead to an erroneous conclusion on the effect of the food. This causes a dilemma for those pets that have significant scratching, since they need immediate relief. In these cases we recommend using medication initially and starting your pet on a hypo-allergenic diet at the same time. If the itching is decreased after 1-2 months you can start weaning your pet off the medication to determine if the scratching is still diminished while on the hypo-allergenic diet also. In some cases we find the use of this food will allow us to use less medication to control the scratching.
Compliance is important, so make sure that everyone that even remotely feeds your pet knows about the diet change. If you give your pet food with medication, or treats, make sure it is not the original food that might have caused some allergy. Some pets need time to make the transition to a new food so be patient. Never let a cat go more than a few days without eating due to potential problem with the liver. Mix their new food in with their original food and make the transition over 7 days.
Obviously, if it is exposure to an allergen that causes the problem in the first place, then logic will dictate that we eliminate this exposure. In reality though, these allergens are everywhere. Minimizing exposure can be beneficial since it will decrease the allergen load, and hopefully keep your pet under the pruritic threshold.
Pets that are allergic to kapok, wool, cotton, feathers, animal dander, newspaper, and tobacco smoke all might benefit from limiting exposure. Limiting the number of houseplants could be helpful, and use synthetic material for your pets bedding. Pets allergic to house dust mites might do better kept out of bedrooms or placed outside more often.
Being outside though might expose them to more pollens. Grass is a common allergen causing skin allergy, so if possible, try to minimize exposure. Keep the grass cut short, and keep pets out of the yard when cutting the grass. Rinse your pet’s feet and face off thoroughly after being exposed to grass can be beneficial in some cases.
Mold allergies might be helped by dusting and cleaning more thoroughly, especially house plants and bathroom carpets. Even think about replacing your carpets with wooden flooring. Keep your pet away from damp areas like basements (in California that’s easy since we don’t have many) and use humidifiers and air conditioners in humid weather. Rinse their filters frequently and clean with chlorine bleach. To truly filter most of the dust, mites, pollens, bacteria, and molds in your house you need to use a HEPA (high efficiency particulate air) filter. Upright vacuum cleaners return most of the dust back into the air, so use canister or cylindric type machines.
Routine and thorough washing, cleaning, and vacuuming of your household will keep mold, house dust, and house dust mites to a minimum. Keep your pet out of the house when doing thorough cleaning and vacuuming to minimize allergens that are stirred up by the cleaning. Put flea powder or a flea collar in the vacuum bag. Put plastic over bedding that might harbor house dust. Keep pets indoors at dusk and early morning during heavy pollen seasons.
Since we live in a flea endemic area year round, we cannot emphasize the importance of proper flea control in any pet that has a skin condition. Even pets that are 100% indoors are possible flea victims. This is especially important in cats, both indoor and outdoor cats.
The products available today are a significant improvement over flea control products in the recent past. They are economical, safe, effective, and very convenient. The product we recommend for dogs is Trifexis©. It prevents fleas, heart worms, and internal parasites, and is given orally instead of a topical gel.
Both of these products are used monthly. In some situations one of our doctors will have you use it more often. We also have detailed brochures on these products.
There are many flea products that also can be used. Some are oral, some are topical, some are long lasting collars. Here are some of our recommendations:
Every pet reacts differently to the medication used in atopy, so we might need to try different ones, at the lowest dose possible, to find the medication, or medications, that work best. Since treatment tends to be long term, so our goal is always to substatntially minimize the itching whilel using as little medication as possible. We use a multmodal approach, utilizing topicals, antibiotics, nutrition, and anti-inflammatories, to give the best possible outcome.
One of the mainstays of therapy for treating atopy is cortisone, commonly know as steroids. These steroids fit in the class of drugs called corticosteroids, which are not the same thing as anabolic steroids used by bodybuilders. Cortisone use is usually reserved for flare-ups, since long term use has the potential for causing side effects. Long term use of high doses of cortisone can lead to hair loss, thinning of the skin, liver problems, stomach problems, and muscle weakness. The overuse of cortisone can also cause iatrogenic Cushing’s disease.
Cortisone is a potent drug used in human and veterinary medicine literally thousands of times each day. Without this drug we would not be able to treat a large number of diseases. Cortisone has been abused by some people, leading to a bad name for this drug in some people’s minds. When used judiciously, and under a doctor’s supervision, it is one of the most important drugs we have. It is our first line of defense when a pet is scratching so severely it is maiming itself.
Cats are more resistant to the side effects of cortisone than dogs. Some cats are difficult to pill, so it is not uncommon to use an injectable version of cortisone that lasts for several weeks to months. Older cats need to be checked for underlying problems like sugar diabetes and heart disease before instituting cortisone therapy. Cortisone will raise the blood sugar level, making it more difficult to control the problem. It can also cause the body to retain more sodium. This is only a problem in a cat that is in congestive heart failure.
Cortisone is usually given on an every other day basis and eventually decrease the dose even further as your pet improves. This minimizes side effects yet still gives an adequate amount of the drug to minimize scratching. In many cases we give an injection first to give your pet immediate relief from the scratching. We routinely use cortisone for 1-2 weeks to help get the scratching problem under control. Since cats are more tolerant to cortisone, and can be difficult to pill, it is not unusual to use the injectable version of cortisone in them.
While on cortisone you will notice that your pet drinks and urinates more than usual. It might also have an increased appetite and might show some behavioral changes. These symptoms will go away, in the meantime make sure your pet has access to fresh water at all times and can go outside to use the bathroom frequently.
Antihistamines can be effective in treatment in some cases. They counteract the release of histamine (that’s why they are called antihistamines) from the mast cell, which as you know is the source of the itching. They are the mainstay of our long term medical treatment for skin allergies. Occasional side effects include drowsiness and dry mouth, both of which tend to resolve. In general, they are safe to use on a long term basis.
We will initiate an antihistamine trial to determine which one, if any, is most effective for your pet. We do a trial for up to 2 weeks to determine if one is effective or not. It is helpful not to have your pet on cortisone at the same time we are trying a new antihistamine, since we will not know if a decrease in pruritus is due the cortisone or the antihistamine. If we find one antihistamine that works well we stay with it on a long term basis. Eventually this might change, and if there is a significant flare up we will use cortisone to control the problem for several weeks. In the long run, even if antihistamine use has only minimal effects on decreasing pruritus, its use can help us decrease the use of cortisone.
Some of the common antihistamines we use are:
Medications used to treat allergic dermatitis are used on a long term basis. We will refill medications as needed, and require a complete physical exam every 6 months to verify we are still treating the correct problem and to check for potential side effects to medication. A blood sample will be recommended periodically to verify the health of internal organs that might be affected by long term medication.
There is a combination antihistamine and cortisone called Temaril-P that has been use for decades. The two drugs in combination haven proven to be highly effective, and since each of these drugs is at a low dose side effects are rare.
A popular remedy we use commonly and successfully is called Temaril-P. The cortisone and antihistamine are in a low dose (trimeparizine -5 mg, prednisolone-2 mg), but when combined in the same medication have the effect of a larger dose. We get the best of both worlds in this case because the low amount of medication means less chance for side effects when used long term. This drug is also effective for pets that are coughing and vomiting.
Some dogs scratch so severely they cause a secondary bacterial infection of the skin called pyoderma. The bacteria that commonly causes this is called Staphylococcus intermedius or pseudointermedius.This secondary bacterial infection intensifies the itching. These dogs need treatment with antibiotics for several weeks to several months. In addition, they need to be bathed with shampoo that will help the skin infection. Long term use of antihistamines are not effective if a skin infection (pyoderma) is allowed to persist.
If a hot spot is present it will be gently clipped and cleansed. Pets with hot spots must be put on antibiotics and usually short term cortisone to prevent the problem from progressing. Hot spots are very painful, and oftentimes require sedation if the wound is to be clipped and cleansed properly.
Antibiotics that work best for pyoderma include:
There is a new version of injectible antibiotic called Convenia that lasts for 2 weeks. This is especially useful in cats due to the difficulty in giving them a pill.
Secondary fungal infections can occur, especially when the feet are licked constantly. The most common one is called Malassezia. It is treated with topical antifungals in most cases.
An effective long term treatment for atopy relies on cyclosporines, the medication that prevents organ transplant rejections. It is called Atopica©
Your dog must weigh at least 4 pounds for it to be used. Its main advantage is the fact it works without any side effects on a long term basis that can be encountered in drugs like cortisone.
It has recently been approved for us in cats in a liquid form
Atopica is highly effective, and we recommend it as one of our important long-term treatments for atopy. It does not contain cortisone so we do not have the side effects associated with cortisone.
Initially it is given once daily for 30 days, and should be given one hour prior or two hours after a meal. If a response is achieved we will decrease the dose slowly, with the ultimate goal of giving it 3X per week. It becomes cost effective at this twice per week dosing, and it is warranted to try this medication if your pet is on chronic cortisone use or you want an effective treatment without cortisone.
There is a relatively new medication available that shows great promise in treating atopy. It’s our fallback medication when the other treatments do not work. We give it for a 10 day trial the first time. Some dogs stop their itching and stay this way for quite a while. Other dogs need to be on Apoquel long term.
It is a member of a class of drugs called Janus Kinase (JAK) inhibitors. It is an immune mediating drug that suppressed cytokine function. Cytokines are implicated in the cause of itchiness (pruritus).
A very small amount of dogs had diarrhea, vomiting, and excess drinking, which went away eventually.
It should not be used in dogs with history of cancer (neoplasia), demodectic mange, or that have severe immunoseppresion. Its simultaneous use with cortisone (prednisone) has not been evaluated.
If an allergy test is performed on your pet we will know what it is allergic to, and allergy shots can be custom designed for your pets specific allergy. Giving allergy shots is called hyposensitization or immunotherapy. Theoretically, hyposensitization stimulates the production of IgG, which subsequently attaches to the allergen, preventing IgE from attaching to this same allergen. If there is no IgE attached to the allergen, then the mast cells do not release histamine.
Even if you do not give the allergy shots, knowing what your pet is allergic to can be beneficial in some cases, assuming you can remove the offending allergen (see previous section on avoidance). We tend to rely on allergy shots when avoidance methods and medication are unsatisfactory in minimizing pruritus.The company that performs the RAST test also supplies us with the allergens to give the allergy shots.
Giving allergy shots can be a significant way to minimize your pets scratching, although just like in people, no guarantee can be given to the outcome. Estimates vary, but in general, you can expect some improvement 60% of the time. In some cases we will still keep your pet on an antihistamine or cortisone, or Atopica©, but at a reduced dose. A decision to undertake this treatment modality takes a commitment to a lifetime of giving these injections in most cases.
Giving the injection is very easy since it is a small amount with a tiny needle. We will teach you how to give them, and if need be, will give them for you. Initially, the injections are given every few days for several months. It takes at least several months to know if the injections are working, and up to a year for full effectiveness. Eventually, they are only given from once every few weeks to only a few times per year. Each pet’s response is different.
Allergens are made specifically for each pet. This dog is allergic to many things, so three vials are needed to treat its problem.
If your pet is kept in a confined area, the use of a room purifier that filters out pollen particles can be of help.
Some allergic dogs and cats scratch less when supplemented with essential fatty acids. Essential fatty acids tend to work best when combined with an antihistamine. The main ones we use are Derm Caps and EFA-Z. As with other therapeutic options, essential fatty acids will not work when the skin has pyoderma. It will take at least several weeks of supplementation to see any improvement. In some cases the need for inflammatory medication will be reduced when a pet is put on essential fatty acids supplementation.
Bathing in cool water several times per week is beneficial. Do not use hot water because it can intensify the itching. Proper bathing will help remove allergens and eliminate dry skin, both factors that affect the pruritic threshold. Bathing your pet too often will dry its skin out and increase its itchiness.
We have many different shampoos that will help you- please ask one of our receptionists to show you. We have had best results with oatmeal shampoos and rinses, along with antihistamine shampoos and rinses. Use a mild shampoo once weekly to keep the hair coat clean without drying it out. For hot spots we use Oxydex shampoo. If we suspect a secondary fungal infection caused by Malassezia we will use an antifungal shampoo called chlorhexidine.
This is an allergic reaction to shampoo in the arm pit area of a 8 month old female pit bull named Pumpernickel. This illustrates the principal that many things can cause an allergic reaction, even treatments for allergies.
There is a strong tendency on the part of pet owners to use topical medications for allergic skin disease. They are used, and are helpful, but should not be relied upon as the primary source of treatment. Topical medications we use usually have an antibiotic, an antihistamine, or cortisone as ingredients. We tend to use topical agents most often when presented with pets with hot spots. In these cases we use antibacterial creme in addition to antibiotics that are given orally.
Allergic Dermatitis is a chronic disease that is not cured, only controlled. It can be the cause of significant frustration, and will wax and wane in some cases. Understanding this disease will help you formulate a long term plan that suits your needs and minimize the chance of side effects when medications are used on a long term basis.