One of the more common conditions encountered in pets, especially as they age, is kidney (renal) disease. This disease is particularly prevalent in older cats, and is called chronic renal failure (CRF). We have information on CRF treatment towards the end of this page if you want to skip right to it.
The kidneys are a very important organ, and do much more than just filter waste products out of the bloodstream. When a pet has chronic kidney disease there are many issues that need to be addressed for a successful outcome to treat. You will learn about them in more detail later in this page. The more important ones are:
- Protein and phosphorous regulation
- XS protein in the urine
- High blood pressure
- Dehydration and electrolyte imbalance
- Low pH in the bloodstream
- Stomach and intestinal ulcers
This page describing kidney disease is very thorough. We have a summary page on kidney disease if that better suits your needs.
Cats that have kidney disease commonly have other problems that need careful attention if the kidney problem is to be treated successfully. Some of these other common problems are hyperthyroidism, heart disease, dental disease, sugar diabetes (diabetes mellitus), and high blood pressure (hypertension) leading to blindness.
Several medical terms are used when describing kidney disease:
|azotemia– excess nitrogenous waste products in the bloodstream||hypophosphatemia– low blood phosphorous|
|hypokalemia– low blood potassium level||hyperphosphatemia– high blood phosphorous|
|hyperkalemia– high blood potassium level||polydypsia– excess drinking|
|anemia– low red blood cells||polyuria– excess urinating|
|BUN– blood urea nitrogen||PU/PD– polyuria and polydypsia|
|GFR– glomerular filtration rate||CRF-chronic renal failure|
|hypertension– high blood pressure||ARF– acute renal failure|
The kidneys are such a vital organ that 25% of the blood that enters the circulatory system from each heartbeat goes directly to the kidneys through the renal artery. With such a high metabolic rate the proper functioning of this organ is critical to health. The high metabolic rate and importance of this organ makes the kidneys susceptible to many problems.
This is the kidney from a cat. It lies in a depression in the abdomen called the retroperitoneal area. You can see the dark liver on the far left, and the renal vein as it leaves the kidney and mergers with the vena cava. The blood from the vena cava flows into the liver and then directly to the heart. This is the blood that has been filtered of impurities and is reentering the circulation. You can not see the renal artery or ureter, they are buried in the white fat at the top of the kidney.
Blood enters the renal artery and flows into the nephron where it is filtered. The blood from the renal artery that has been filtered now flows out of the renal vein where it goes back into the circulatory system. The impurities that the nephron filters out of the blood collect in the renal pelvis and eventually out into the ureter in the form of urine.
The primary functional unit of the kidney is the nephron. Each kidney has upwards of one million nephrons, so obviously they are microscopic in size. Every nephron is a self contained unit that can form urine by itself. Not all nephrons are used at the same time, which gives the kidneys the capacity to increase their workload if called upon. This reserve capacity is lost when chronic renal failure occurs. These pets (especially cats) outwardly appear normal, but have greatly reduced ability to adapt to changing physiologic needs. Being chased by a dog, not having enough water to drink, etc., can send them into renal failure.
This is how it looks in a real kidney from a cat
This is a kidney, turned sideways compared to the one above, as we view it with the ultrasound. The yellow line is measuring its length.
The important anatomical components of the nephron are described below:
This small artery is one of the many small branches that come off the renal artery as it enters the kidney. It supplies the glomerulus with blood. Eventually filtered blood returns to the renal vein.
This is a collection of many small blood vessels at the end of the afferent arteriole. Normal pressure of the blood in the glomerulus causes fluid to flow into a collecting area called Bowman’s capsule.
Fluid that collects in Bowman’s Capsule eventually flows into the tubules. It is in these tubules that waste products and excess electrolytes are filtered out of the fluid, and normal blood constituents like protein and glucose are absorbed back into the bloodstream. When a diuretic like Lasix is given it acts on these structures.
At the end of the tubules is the collecting duct, where the urine produced starts to flow out of the nephron. Other nephrons deposit urine in collecting ducts as these ducts flow into the renal pelvis. From the pelvis the urine flows into the ureter and bladder.
The kidneys are located in a specific area of the abdomen called the retroperitoneum. This area is a small indentation at the top of the abdomen just underneath the spinal vertebrae. It affords protection to this vital organ.
The kidneys have a profound affect on almost all the physiologic processes of the body. The mechanism by which the kidneys perform these functions is extremely complex, the most important of which will be summarized:
In relation to the kidneys, the brain monitors bloodstream levels of water, waste products, electrolytes, and red blood cells. The circulatory system also has receptors like the brain to monitor blood volume also. If the water level is too low, as occurs with dehydration, the brain secretes more of a hormone, called ADH (anti-diuretic hormone), into the bloodstream.
As a result, the kidneys excrete less water into the urinary tract, retaining more fluid in the bloodstream to counteract the dehydration. The brain also increases thirst simultaneously. The end result is less urination. The urine that does get excreted is more yellow than usual due to a greater concentration of waste products being excreted in relation to the amount of water being excreted. The only thing we notice is that we urinate less and it is more yellow in color.
As we drink water to quench our thirst and rehydrate, the body notes this change and the brain secretes less of the hormone called ADH. Now when we urinate more water is excreted by the kidneys, and our urination occurs with a dilute urine in greater quantity. So, the ability to concentrate the urine and dilute the urine is an important function of the kidneys. It is a fine tuned mechanism that is closely regulated to maintain optimum amounts of fluid in the bloodstream and organs.
As a fun fact, it is the inhibition of ADH by alcohol’s depression effects on the brain that causes excess urination when drinking alcoholic beverages. Eventually this excess urination causes dehydration, leading to that inevitable curse called a hangover.
The kidneys also secrete a hormone called renin. Through a complicated set of biochemical pathways this ultimately leads to an increase in salt (sodium) in the bloodstream. Sodium pulls water towards it, so more sodium means more fluid in the bloodstream. It will have an effect on blood pressure, which you will learn about later.
Waste Product Regulation
The brain also monitors waste products that build up in the bloodstream. These waste products are the end product of normal metabolic processes, especially the metabolism of proteins. They are called nitrogenous waste products, and are measured by a blood parameter called blood urea nitrogen (BUN). Another waste product that is closely regulated by the brain and kidneys is called creatinine. It is the end product of the metabolism of muscle.
The kidneys also excrete toxins and foreign substances that are introduced into the body. Almost every medication given, either orally or by injection, is eliminated to some degree by the kidneys.
The rate at which fluid flows into the glomerulus is important. This is called the glomerular filtration rate (GFR), and is measured in ml/minute. Too small a flow and waste products are not eliminated, a problem encountered during dehydration. Too much flow and normal blood constituents like protein are excreted when they shouldn’t be.
Electrolytes are also of importance in relation to the kidneys. Sodium is of extreme importance in the normal functioning of all cells. It allows nerve impulses to occur and is critical in the regulation of water levels in the bloodstream. Through the release of a hormone called angiotensin the kidneys regulate fluids levels of sodium in the bloodstream. This has a major affect on the blood pressure. Potassium is also a critical electrolyte. Potassium levels need to be kept at a very narrow range to prevent serious consequences like heart irregularities.
The kidneys also regulate calcium and phosphorous by hormones called calcitrol and parathyroid hormone, and by regulating vitamin D. Vitamin D allows the absorption of calcium from the intestines. If the kidney disease progresses long enough the excess secretion of parathyroid hormone causes the bones to become swollen and fibrous as the body attempts to maintain a normal calcium level. This is called renal osteodystrophy.
As the bones become more fibrous the marrow is not able to produce red blood cells as effectively. This leads to weak and thin bones, as evidenced by a swollen face and jaw as the bones of the lower jaw weaken. It can occur in other bones also. This is similar to what occurs in reptiles when they get bone disease. You can see a picture of the swollen jaw of an Iguana with bone disease. Don’t forget to come back here because we are only just getting going.
The pH of the bloodstream, which is a measure of acidity, is another important area of kidney physiology. The kidney regulates this acidity by excreting excessive hydrogen ions and the selective secretion and reabsorption of bicarbonate.
Red Blood Cell Production
The kidneys secrete a hormone called erythropoeitin into the bloodstream. This hormone circulates to the bone marrow and stimulates it to produce red blood cells. A lack of adequate levels of this hormone will cause anemia. Toxic waste products that build up in the bloodstream decrease the life span of a typical red blood cell, further exacerbating the anemia. And, as you already learned above in hormone regulation, the fibrous bones have less bone marrow. There can even be clotting problems due to a low number of platelets.
Over the course of days, weeks, or months, normal nephrons get replaced with scar tissue, and become nonfunctional. When this occurs to approximately 75% of the nephrons the kidneys no longer have the ability to respond to the needs of the body. There is no longer any reserve, and all of the remaining nephrons are working full time. These remaining nephrons swell (called hypertrophy) to adapt to this increased workload. This allows them to adapt and selectively excrete or reabsorb important nutrients.
Eventually these remaining nephrons cannot keep up, and it leads to a buildup of nitrogenous waste products (called azotemia) in the bloodstream. The body compensates by increasing thirst, which causes PU/PD, and the waste products get flushed out of the bloodstream and into the urine.
Unfortunately, flushing out the waste products in bloodstream with excess thirst also flushes out important electrolytes and protein into the urine. This causes weight loss and weakness as the kidneys continue to deteriorate. The excess urination that occurs as the body tries to rid itself of these excess waste products can also cause dehydration.
Oral ulcers occur when bacteria in the mouth convert the extra uremic waste products to ammonia. Waste products that buildup in the bloodstream also have an effect on the bacteria in the mouth and exacerbate gingival and periodontal disease. The waste products also change the pH of the bloodstream and cause ulcers in the stomach and intestines. This causes vomiting (emesis), loss of appetite (anorexia) and weight loss. Ulcers can also be found in the mouth and tongue due to the uremia.
Hormones are affected and phosphorous builds up in the bloodstream further adding to a pet’s woes. Eventually calcium is deposited in abnormal places, and can lead to problems with many skeletal and internal organ problems. Due to sodium imbalance, hypertension (high blood pressure) can develop. Hypertension occurs in a high percentage of animals with kidney disease.
As the kidneys continue to deteriorate erythropoetin is not secreted in adequate quantity and anemia results. This anemia also makes a pet weak and adds to the anorexia that is usually present.
The nervous system is affected by all of these problems. If the uremia is severe enough hypothermia and seizures can result.
Acute Renal Failure (ARF)
This is a serious form of kidney disease that commonly leads to death. The kidneys have an abrupt decrease in the GFR due to a toxin or loss of adequate blood supply (called ischemia). Many different disease processes can cause ARF, including anesthesia for any surgical procedure. That is why we give intravenous fluids (IV) to almost every surgical case.
Chronic Renal Failure (CRF)
This is the most common form of kidney disease we encounter, particularly in older cats. It tends to develop more slowly than ARF, so the body has time to institute corrective factors (called homeostasis) to compensate for the problem. Unfortunately, these corrective factors tend to hide early symptoms of disease. Consequently, treatment is not initiated as soon as it might be. Again, as in many diseases we encounter, this drives home the fact that pets over 8 years of age should have annual physical exams along with blood and urine samples.
Pets in CRF that have lost their ability to compensate for their failing kidneys can be presented to us in an acute phase, similar to ARF.
The are a multitude of causes to kidney disease. Some of these cause ARF, while others cause CRF. In some cases, ARF can progress to CRF.
Many drugs that are used on a day to day basis can be toxic to the kidneys:
- snake and bee venom
- heavy metals
- cancer chemotherapeutic agents
- aspirin and antinflammatories
- anti parasite drugs
- blood pressure medication
The outcome of exposure to these toxins depends on a pet’s age, other disease processes that might be present, any medication your pet is currently taking, how long there has been an exposure and at what dose, along with the specific toxin. In some cases they are treated with supportive care like intravenous (IV) fluids. Other cases are treated with specific antidotes.
Some toxins, notably antifreeze ( 95% ethylene glycol) are catastrophic to the kidneys. Antifreeze is very sweet tasting and is readily licked by both dogs and cats if it spills on the ground when car antifreeze is changed. Ethylene glycol is converted in the liver and kidney to a toxic metabolite that changes the pH of the bloodstream and destroys the kidneys by depositing calcium oxalate crystals in the renal tubules.
It is a medical emergency and requires specific and immediate measures if the kidneys are to be saved. Unfortunately, unless a pet owner actually observes their pet licking antifreeze, they don’t bring their pet in for care until it is very ill. In this situation the prognosis is grave, and death is common. If treated within a few hours of ingestion the prognosis for recovery is much better.
This disease has several distinct phases:
This occurs during the first 12 hours after ingestion. Pets will vomit, drink and urinate excessively (PU/PD), and appear intoxicated. It is at this stage that observant owners might bring their pet in for an exam.
This stage occurs 12-24 hours after ingestion. Symptoms are vague and pets appear to recover.
This stage appears 24-72 hours after ingestion. Pets in this stage are severely depressed, are not eating, are vomiting, and are not producing urine. When this stage appears death is imminent.
Treatment needs to be given early in the disease to be effective. Inducing vomiting and flushing the stomach out can be very helpful if performed within 1-2 hours of ingestion of antifreeze.
Intravenous fluids and diuretics are also given to maintain normal kidney function by keeping an adequate GFR. Sodium bicarbonate is given to maintain a proper pH of the bloodstream.
Antidotes are given and can be highly effective if given early enough. In cats we give them ethyl alcohol (vodka) intravenously, and literally make them drunk. The vodka prevents the liver from converting the ethylene glycol to the toxic metabolites that destroy the renal tubules. This treatment is used in dogs also.
A better antidote, that works in dogs only, is called Antizol. It is an expensive medication, but it can literally save your dogs life.
Fortunately, the antifreeze manufacturers have added a bitter taste and we do not see this disease anywhere near as commonly.
Cancer of the kidneys can occur even at a young age, although it is usually diagnosed in older pets. Sometimes it arises from the kidneys (primary), much more often the cancer has spread to the kidneys from a different organ (secondary or metastatic). When primary cancer does occur it is often malignant. Fortunately, primary renal tumors are rare. Cancer of the kidneys occurs more in cats than in dogs.
- Lymphosarcoma- Tthis is the most common renal tumor in the cat. Cats with renal lymphoma are commonly positive for the FeLV.
- Adenocarcinoma- The next most common renal tumor in the cat
- Transitional cell carcinoma
- Mast cell tumor
Poor perfusion means inadequate flow of blood through the kidneys, which decreases the GFR. This lack of blood flow prevents the kidneys from eliminating waste products and toxins buildup in the bloodstream. This lack of perfusion is the main pathology leading to ARF.
Heart Disease- If the heart is weak it can not pump enough blood to the kidneys to keep them properly perfused.
Drugs- Some medications can cause constriction of the artery to each kidney with a resulting lack of perfusion
Dehydration- Inadequate fluid in the circulatory system will cause poor perfusion. Dehydration is the most common cause of poor perfusion.
They can put pressure on normal kidney tissue and compromise the filtering ability of the nephron. These tend to be found in older male cats. When there are no symptoms they are sometimes found accidentally when checking for other problems. This is called an incidental finding. When symptoms are present, they can be mild and treated easily by drainage, or there might be compromise with the normal filtering ability of the kidneys.
A specific form of cyst, called Polycystic Kidney Disease (PKD), is inherited in Persian and other long haired cats. Cysts will occur in both kidneys and will lead to CRF eventually as they enlarge and decrease functional renal tissue. The best way to make this diagnosis is with ultrasound. Ultrasound should be used on the offspring of adult cats with PKD and before any symptoms appear.
Immune System Diseases
Bacteria, viruses, cancer, and diseases of internal organs can all set off a reaction where the immune system can interfere with the ability of the kidneys to filter properly. This is sometimes called glomerulonephritis. Symptoms range from mild early in the disease to all the signs associated with kidney failure. A common method of diagnosis is excess protein in the urine (proteinuria) and a lack of protein in the bloodstream (hypoalbuminemia).We use ultrasound at our hospital to help in this diagnosis.
Treatment depends on the exact cause. It might include anti-immune system drugs, aspirin, dietary change, medication to decrease blood pressure, salt reduction, IV fluids, and diuretics.
There are 3 main parasites that invade the urinary tract and affect the kidneys:
They are threadlike worms that affect the kidneys, bladder, and urethra. Eggs of this worm that are passed in the urine are eaten by earthworms, which are then eaten by dogs to complete the cycle. In some dogs there are no symptoms, while in others there might be blood in the urine (hematuria), difficult urinating (dysuria), or urinating small amounts (pollakuria). This parasite is diagnosed by finding the egg in a urine sample. In most cases the disease goes away by itself within 4 months, although it can be treated. Prevention of recurring cases relies upon removal of surfaces that could harbor earthworms.
This is an uncommon parasite in our area that invades the urinary bladder of cats. Usually there are no symptoms, and the disease routinely resolves by itself within 4 months.
This parasite resides in the kidney or abdomen near the kidneys, although they have been found in the urinary bladder, urethra, ovary, uterus, and pericardium. It causes a gradual deterioration of the kidneys.
Eggs from this parasite are passed through the urine and eaten by aquatic annelids. Dogs get this parasite from eating raw fish and frogs that have eaten the aquatic annelids.
Sometimes there are no symptoms until there has been significant kidney destruction. They are diagnosed by finding the egg of the parasite in abdominal fluid or in the urine. Treatment involves surgical removal of the worms from the kidneys or abdomen.
They are difficult to control because the eggs can live in the environment for a long time. Dogs should be prevented from eating frogs and raw fish. It is possible for humans to get this disease from eating raw fish or frogs also.
The FeLV and FIP can affect the kidneys. These viruses are prevalent in the cat world, and cause significant problems. We do not see these diseases commonly any more, especially FeLV. This is a testament to the use of vaccines.
They can ascend from the lower urinary tract and cause dysfunction in the kidneys. Leptospirosis is a specific bacteria that affects the kidneys, seen almost exclusively in dogs. Dogs get it by direct contact with infected urine through their mucous membranes. It also affects the liver.
In severe cases a dog can go into shock and rapidly die from Leptospirosis. In some cases they are sick with a fever, depression, vomiting, diarrhea, and poor appetite. There might also be muscle pain, eye problems, and respiratory problems. Most cases are chronic and might not show many symptoms.
There is a vaccine to prevent this disease which is a routine part of our DHLPP vaccine. The vaccine is highly effective in preventing this disease.
Bacteria can also cause pyelonephritis, an infection of the renal pelvis. The following bacteria are implicated:
- E. coli
- Staph. aureus
- Proteus mirabalis
- Strep. spp.
- Klebsiella pneumonia
- Psuedomonas aeruginosa
- Enterobacter spp.
These bacteria usually ascend from the lower urinary tract. Occasionally they enter the kidney from the bloodstream. Their presence can cause constriction of the blood supply to the kidneys and destroy normal kidney tissue when attacked by the immune system. They can eventually lead to kidney failure.
These bacteria can cause ARF or CRF. Symptoms include fever, depression, lack of appetite, pain, PU/PD, and weight loss. In the chronic version sometimes there are no symptoms at all. They are treated with antibiotics for a minimum of 4 weeks, along with supportive care.
This is the deposition of fibrous protein cells in the glomerulus that interfere with the kidneys’ ability to filter. Amyloid causes the kidneys to become small and irregular. Pets with amyloidosis have typical symptoms of kidney disease.
Most dogs are middle aged or older, and it is seen in abyssinian cats and Shar Pei dogs. It is diagnosed by proteinuria, just like the immune system diseases that affect the kidney. Amyloid can be deposited slowly allowing a long life, or it can occur rapidly leading to early death. There is no specific treatment except routine supportive care of the kidneys.
One of the more common causes of kidney trauma is when a pet is hit by a car. These injuries can be serious and easily lead to death. Radiography is helpful in making this diagnosis, although special x-rays or ultrasound might be needed to know for sure.
This is a bruised kidney from a cat that was attacked by a dog. The bruise covers over 1/3 of the kidney. This is a fatal lesion.
The symptoms that occur depend mainly on how long the problem has been present and the specific reason the kidney failed in the first place. Some of the more common ones you might notice at home are:
Excess urinating and drinking
This is known as polyuria/polydypsia (abbreviated PU/PD). It is by far the most consistent symptom of kidney disease. PU/PD also occurs in sugar diabetes and hyperthyroidism to name a few, so the diagnostic process needs to be followed to make an accurate diagnosis of a pet with symptoms of PU/PD. If you suspect your pet of having PU/PD you should measure how much water it drinks each day and look for a changing trend.
In ARF there might not be any urination (called anuria) at all. This is an extreme emergency. Two of the more common causes are antifreeze poisoning and male cats with urinary tract disease that have a plugged urethra.
Weight loss occurs due to poor appetite and the loss of protein as the kidneys attempt to flush toxins out of the body.
Poor appetite (anorexia)
The buildup of toxins, electrolyte imbalances, dehydration, and even anemia are the causes of a poor appetite in kidney disease. This is one of the most common reasons pet owners bring their cats to us when renal failure is the cause. Ulcers in the mouth and stomach add to this problem. Sometimes its a wonder that cats with moderate to severe kidney disease even eat at all.
Dehydration and poor appetite add to weakness. An imbalance of a specific electrolyte called potassium adds significantly to weakness. This is the reason we sometimes add supplemental potassium to the fluids we give pets with kidney disease and also why we supplement them with oral potassium.
The buildup of toxins is a big cause of the vomiting. Vomiting causes further dehydration and loss of potassium, further exacerbating the problem in pets with kidney disease.
If uremia is severe enough the brain can be affected by the toxins that build up.
If the waste products are not being eliminated adequately the buildup of toxins can cause ulceration. These ulcers are prevalent in the digestive system, especially the stomach, and might necessitate medication.
The tip of the tongue of this cat has an ulceration due to kidney disease. Oral ulcers are due to the breakdown of urea present in saliva to ammonia by bacteria found in the mouth. There are other causes of ulceration, including trauma, biting electrical cords, poisons, and viruses.
Blindness can occur due to the high blood pressure (hypertension) that develops as a consequence of CRF. We start therapy in cats when the systolic blood pressure consistently exceeds 160 mm Hg. Diastolic blood pressure is of no clinical use in the cat.
It can be difficult to get a consistent blood pressure reading in cats due to their stressful nature at our hospital. We will repeat the test numerous times, in a calm and quite environment, to make sure the readings are accurate.
The dilated pupils from this 15 year old cat with CRF are due to blindness.
Checking a cat for high blood pressure (called Hypertension) is not as simple as in a human. Specialized equipment is needed, including a doppler ultrasound.
Since the symptoms of kidney disease mimic the symptoms of other diseases a thorough approach is needed to differentiate them. 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 also encountered in pets that have renal disease. Unfortunately, it is difficult to diagnose acute renal failure early in the course of disease.
Kidney disease can occur at any age. If it occurs at a young age we tend to think more of toxins, cysts, and trauma. The most common form of kidney disease, CRF, occurs mostly in older pets.
Several feline breeds are prone to getting CRF as they age:
- Maine Coon
- Russian Blue
Certain canine breeds are also prone to CRF:
- Shih Tzu
- Lhasa apso
- Shar Pei
Kidney disease is suspected in any pet that has some of the symptoms described above, especially PU/PD. The recent administration of medication, a recent bout of a disease, the changing of antifreeze, especially in the fall , and recent administration of anesthesia, are all helpful clues. Pets that have other diseases that can affect the kidneys, notably heart disease, and hyperthyroidism, alert us to the potential for kidney disease.
Symptoms noted during a physical exam depend on what caused the kidney’s to fail, how long the disease process has been present and whether a pet has the acute form or chronic form of the disease.
Physical exam findings might include:
- Pale gums due to anemia. You can check for pale games at home. Our Learning Center shows you how.
- Small and irregular kidneys upon abdominal palpation if CRF is present
- Large or nodular kidneys if a cyst or cancer is present
- Enlarged lymph nodes
- Dilated or uneven pupils
This older cat has kidney disease causing low potassium (hypokelemia). If the low potassium is severe enough a cat might have this neck posture.
Kidney disease can only be diagnosed with appropriate tests. As a general rule, we recommend screening for kidney disease by running a blood panel and a urinalysis on all pets greater than 8 years of age. We also screen for other diseases, notably liver disease, sugar diabetes, and hyperthyroidism, on this blood panel due to their prevalence in older pets.
Lymph node biopsy
Peripheral lymph nodes can be palpated in numerous locations. They can enlarge for several reasons, one of the more important ones is cancer. If they are enlarged and significant disease process is suspected then one of them is biopsied (example to follow).
An important tool in the diagnosis of kidney disease is a blood panel. We look for abnormalities in several specific tests:
BUN- Blood Urea Nitrogen
The BUN is usually elevated in pets with kidney disease. It can also elevate in dehydrated pets and in pets with an obstructed urethra causing an inability to urinate.
If a urinary obstruction is the cause of an elevated BUN, called post renal uremia, the BUN levels tend to be extremely high. If dehydration is the cause of the elevated BUN, then the values do not tend to be as high. The BUN must be interpreted in conjunction with a urine test called specific gravity to know if the BUN is elevated due to kidney disease or dehydration. Liver disease and nutrition can also influence the level of BUN.
It is a very accurate way to diagnose kidney disease, and is more reliable than BUN since factors like dehydration are not as influential on creatinine as they are on BUN.
This test is also a good early indicator of kidney disease even when normal if the trend in values is increasing. This again emphasizes the importance of yearly wellness exams as your pet ages. If the creatinine is going up, even if in the normal range, we might start treating for a kidney problem much earlier in the course of the disease.
In the more advanced stages of kidney disease the phosphorous levels elevate. This is not a good prognosis.
This is an enzyme produced by the pancreas to aid in the digestion of carbohydrates. It is excreted by the kidneys, so an excess in the bloodstream could indicate kidney disease
Serum symmetric dimethlyarginine is a new kidney marker that might aid in early diagnosis of this malady. Increases in this test occur prior to increases in serum creatinine if a normal creatinine is considered 2.4 or less.
Red Blood Cells
The kidneys produce a hormone called erythropoeitin that stimulates the bone marrow to produce red blood cells. Anemia occurs in kidney disease due to inadequate levels of erythropoietin, shortened survival time of red blood cells in general, bleeding in the stomach or intestines, and the effects of uremic toxins on parathyroid hormone. Pets that are dehydrated might not show anemia on a blood sample until they are rehydrated.
This dog has white gums in addition to the severe dental disease that is present. The white gums are due to anemia from CRF.
This is an actual blood panel from a typical pet with severe CRF. The 3 most important tests on this panel are highlighted in yellow, along with their normal values on the right.
This is also an important tool in the diagnosis of kidney disease and another early indicator of kidney disease along with creatine. Changes in several parameters could indicate kidney disease:
Specific Gravity (S.G.)
The ability of the kidneys to dilute and concentrate the urine is an important parameter to monitor. Water has a specific gravity of 1.000. A pet with kidney failure has a specific gravity of between 1.008-1.012. A specific gravity in this abnormal range is called isosthenuria. In cats with normal kidney function, the S.G. should be greater than 1.035, in dogs it should be greater than 1.025.
This number is interpreted in conjunction with the BUN to help determine if the elevation in BUN is due to dehydration or kidney disease. To complicate things further, dehydration and kidney disease can occur simultaneously. Also, as mentioned above, liver disease, a common problem in older pets, can also be an influence.
To be accurate the specific gravity needs to be checked immediately after obtaining a urine sample.
Excess protein in the urine, called proteinuria, is a common finding in CRF. It can also occur in glomerulonephritis, pyelonephritis and amyloidosis. There is evidence to suggest that urine protein:creatinine ratio can be a predictor of survival time. Cats with a ration < 0.4 tend to live significantly longer than cats with a ratio > 0.4.
Specific types of cells, called casts, can also be an indication of kidney disease.
This urine sample is from the cat with the blood sample shown above. The S.G. is very low, and since this cat has a high BUN, the problem is most likely due to CRF. Fortunately for this cat there are no other serious abnormalities on this urine sample.
Urine Culture and Sensitivity
If pyelonephritis is suspected, or bacteria are noted in the urinalysis, the urine should be cultured to determine which bacteria if any is present. If a bacteria is grown out then the appropriate antibiotic should be used for 4-6 weeks.
Radiography can be very helpful in the diagnosis of kidney disease. It allows us to visualize the kidneys, check for stones in the urinary system, look for calcification that might go along with kidney disease, and also look at other organs that commonly have a problem as pets age.
These kidneys have a normal size and shape. Use this for comparison purposes as you look at the other radiographs.
This is the radiograph of a cat with normal kidney’s that is laying on its right side. The right kidney (RK) usually lies forward in the abdomen compared to the left kidney (LK). The area of the 2 kidney’s that overlaps is more whitish in nature.
This is the radiographic of a cat with renal lymphosarcoma (malignant cancer). The diseased kidney is the large white circular area in the center of this view. It is pushing the large intestine down.
Here is different cat with renal lymphosarcoma. It is a different view from the one above. Both kidneys ( K ) are involved in this cat.
A very valuable tool in the diagnosis of kidney disease is ultrasound. It allows us to look at the internal anatomy of the kidney, measure kidney size, and take a biopsy for an accurate diagnosis. In many cases the use of ultrasound precludes us from having to perform an exploratory surgery.
These ultrasound pictures are from the first cat above with the enlarged kidneys. The first picture shows a normal right kidney. Its measurements are 2.3 cm by 3.6 cm.
The 2nd image shows the large and cancerous kidney, measuring 4.6 cm by 7.3 cm. A biopsy was taken from this kidney to confirm the diagnosis of renal lymphosarcoma.
This special test, also know as an IVP (intravenous pyelogram) gives us significant information about the renal system. It has to be used carefully if ARF or CRF is suspected because it can exacerbate the problem. A radiopaque dye is injected into the bloodstream and radiographs are taken of the dye as it passes through the kidneys, ureters, and bladder.
This picture shows how the dye outlines the center of each kidney, called the renal pelvis (remember the renal pelvis in the anatomy picture at the beginning of this page?).
Exploratory surgery (laparotomy) is frequently used as an aid in the diagnosis and treatment of renal disease, especially cancer. We use this option when we feel that ultrasound will not be advantageous.
The arrow points to a lump on the surface of a kidney. It was caused by cancer that spread from the stomach.
A section of the lump was biopsied during surgery to determine the cause. The tremendous blood supply to the capsule that surrounds kidneys can easily be visualized. Even though this capsular blood supply is extensive, it pales in comparison to the amount of blood that flows into and out of the kidneys through the renal artery and veins.
Three sutures were placed in the kidney capsule to control the bleeding that occurred at the biopsy site
A biopsy of a lymph node (called cranial mesenteric) located in the center of the abdomen was also obtained. This helps us determine if the cancer has spread.
Acute Renal Failure
This form of renal disease needs immediate and aggressive treatment to prevent death. In some instances we will send you to a referral center that has dialysis equipment to filter the blood of waste products while your pet’s kidneys recupterate.
Cats that have a urinary obstruction need to be unblocked immediately. If not, excess potassium in the bloodstream (hyperkalemia) can cause death to to its affects on the heart.
Any drug suspected of causing the problem is stopped immediately, and underlying problems are addressed. Fluid therapy is critical, and consists of saline and dextrose solutions initially. Fluid therapy corrects fluid and electrolyte imbalances, increases the blood flow to the kidneys, and starts the process of diuresis.
Cats need to maintain their caloric input in order to minimize the metabolism of protein for their caloric needs. Metabolizing excess of amounts of protein will increase uremia, causing a further deterioration in condition.
Pets that are still not urinating after this initial fluid therapy are given Lasix or mannitol. Excess potassium (hyperkalemia) is a common finding in ARF. If mild, fluid therapy alone should correct the problem. If severe, regular insulin and sodium bicarbonate are used. Pets with ARF are sensitive to ulcers and infections, so treatment for these problems is sometimes initiated.Ethylene glycol (antifreeze) poisoning is an example of ARF.
Pets that have heart disease are sensitive to IV fluids because excess amounts can cause an overload to the lungs called pulmonary edema. These pets pose a dilemma. If we do not give them enough fluids the kidney problem will worsen. If we give enough fluids to help flush the waste products out of the bloodstream, these same fluids might cause pulmonary edema.
This radiograph is of the chest of a normal dog. The heart (H), windpipe (W), and lungs (L) are labeled. The lungs are black because they are filled with air. This is how normal lungs look on a radiograph.
This dog has pulmonary edema. The air filled lungs are no longer black, they are white from the fluid that has built up. This is a very serious condition.
This is the version of kidney disease we encounter most often. The prognosis is guarded, and depends significantly on how long the disease process has been present along with your pet’s age. Pets (usually geriatric) that have other diseases that are common at this age can make this difficult to treat if not caught early enough.
Many pets (especially cats) that are brought to our hospital have CRF that has progressed to the point where the problem has become similar to ARF. These pets need to be hospitalized and put on intravenous fluids almost continuously to get them over this acute phase. We will closely monitor their BUN and creatinine before therapy is instituted and during hospitalization, to ascertain if their kidneys are responding to fluid therapy. If the BUN and creatinine do not drop significantly after 24-48 hours of intravenous fluids then the prognosis for recovery is poor.
Many treatments have been advocated to help minimize the symptoms of CRF (also called the uremic syndrome). None of them can cure the problem, and not all of them have proven to work, so it is important that we tailor make each pet’s therapy to its individual needs. In addition, indiscriminate use of medication to treat a perceived problem can make the kidney disease worse. This applies to almost every drug, since the kidneys are so intimatley invovled in the metabolism of drugs. The medical axiom of “first do no harm” applies directy to kidney disease.
Medical management of CRF needs to address the following:
Protein and phosphorous regulation
XS protein in the urine
High blood pressure
Dehydration and electrolyte imbalance
Low pH in the bloodstream
Stomach and intestinal ulcers
It is sometimes easy to forget some of the more common sense remedies that are available to treat diseases, especially true in kidney disease with all the web sites and advice from people who have encountered this common problem.
Fresh water should be available at all times for your cat. You should fill the water bowl at least 3 times per day to help stimulate drinking. Undue stress should also be minimized at all times also.
Pets with CRF need to be fed a diet that has limited amount of high quality protein. Less protein in the diet leads to less work the kidneys have to perform by removing the nitrogenous waste products that are the end result of protein metabolism. Protein is vital to all bodily functions and can not be indiscriminately limited. As a matter of fact, if protein restriction is not implemented carefully it can make the uremic syndrome worse.
High quality protein means that it contains more essential amino acids, which are those the body cannot produce and must be obtained in the diet. The commercial food that we recommend for kidney disease is called K/D©. It is made by Hills© and is available only from a veterinarian because it is used to treat a specific disease. In addition to high quality protein it also has less phosphorous and sodium.
This food is the gold standard for CRF, and has been used successfully for decades to slow down the progression of CRF.
Most cats take readily to K/D, although it can sometimes be difficult to change the diet on an older cat. Many of the cats are eating poorly and have already lost weight due to the kidney disease, so we don’t want to add to their problem by feeding a diet they won’t eat. Mixing this new food in partially with the regular diet and heating it up a little (for the canned food) in the microwave helps. adding a small amount of a tasty fluid like clam juice can make it taste better.
It is better to have a cat eat anything than to have a cat that won’t eat anything, even if that diet is made to help the kidneys. Sometimes the best we ca hope for is to mix some K/D in with whatever food it ate prior to its diagnosis of CRF.
Water soluble vitamins (ex.- B-complex vitamins) are easily depleted in a pet that has PU/PD. Supplementation can be helpful.
Do not use foods that are lableled “for urinary health”. They are treating a different problem called FLUTD. These foods change the pH of the bloodstream in a way that is detrimental to the kidneys.
Phosphorous lowering medication
Pets with CRF might have an increase in their phosphorous levels as the disease progresses. This excess phosphorous can add to the anemia that is common with CRF. It will also dramatically influence calcium metabolism in the body through a hormone called parathyroid hormone. The end result will be painful calcium deposits in the bones and internal organs, including the kidneys.
Antacid type medications will bind to the phosphorous and keep the level in the bloodstream down. We use amphogel© because it is readily available over the counter, it is a liquid, and cats tolerate it well. As already mentioned, K/D©is restricted in phosphorous, and should be used in combination with phosphorous binding medication.
Potassium increasing medication
Pets with CRF will have a decrease in their potassium levels as the disease progresses. This does not always show up on a blood panel. Using oral supplements and adding additional potassium to fluids helps counteract this problem. Oral potassium is called Tumil-K©, and it comes in a paste for easier administration.
Urine protein reducing medication
Reducing protein in the urine is believed to help slow down the progression of the disease. ACE (Angiotensin Converting Enzyme) inhibitors (ex- Enalapril) or ARB’s (Angiotensin Receptor Blockers) are used when the urine protein:creatine ratio is greater than 0.5 in the dog and greater than 0.4 in the cat. These drugs are given for 2 months and then the urine is checked to see if there is either a 50% reduction from the original test, or if the ratio is below 0.5 in the dog and 0.4 in the cat.
Anemia fighting medication- Darbopentin
One of the long term affects of CRF is anemia due to a lack of erythropoietin secretion from the kidneys. This hormone can be supplemented to help minimize anemia.
One of the most important treatments for CRF is the administration of supplemental fluids. Whenever we tell people their pet with kidney disease needs fluids they commonly respond “its OK, he/she already drinks a lot of water”. Unfortunately, this excess drinking of water is a result of kidney disease, and not a sign that the pet is drinking adequate amounts of water. Cats in particular are not good drinkers, and need additional water to what they are already drinking.
If your pet is hospitalized we will give them intravenously (IV) because of greater effectiveness and accuracy. If your pet responds to IV fluids during its hospitalization we will initiate the use of subcutaneous (SQ.) fluids at home on a daily basis.
This area of home treatment is so important that we have devoted a complete page to its use. Please click here to learn about the proper technique, then return to this section for more treatment options.
Most cats with CRF should receive between 50 ml and 100 ml of SQ fluids at least several times per week. As the problem progresses it will become necessary to give this fluid on a daily basis. We commonly add B-complex vitamins to the fluid bag since these water soluble vitamins are excreted the more we give supplemental fluids. Feeding a food designed for kidney disease like K/D will also help minimize the depletion of water soluble vitamins.
Blood pressure medications
Hypertension is a common occurrence as the disease progresses. Blood pressure lowering medications like Norvasc (calcium channel blocker) and Enalapril (ACE ihnibitor) will help counteract this problem. All cats initially diagnosed with CRF should have a blood pressure taken. It should be rechecked at least every 6 months.
Some cats might respond to ACE inhibitors to decrease the protein in their urine. Further studies are needed in this area to determine efficacy.
Some cats with CRF don’t eat well because of nausea due to excess hormone secretion in the stomach. Tagamet or famotidine is used to counteract this problem. If we suspect an ulcer in the stomach due to the toxins that have built up we will use Tagamet also.
Vomiting is a common problem in pets with CRF. It occurs as a result of uremic toxin buildup in the bloodstream and alterations in hormones that regulate gastric secretions. Vomiting will cause dehydration, leading to a decreased flow of blood to the kidneys (decreased GFR) and an increase in azotemia. We use a drug called Reglan or Cerenia to alleviate vomiting symptoms.
Animals weakend by kidney disease are more susceptible to infection. These pets are commonly older and have significant dental disease. Antibiotics help them fight off infections. The antibiotic dose might have to be adjusted since many of them are removed from the body by the kidneys.
There are other supplements and medications used in CRF that might be of some benefit, although this is unproven. As long as they do not cause the problem to worsen they might be worth trying.
Appetite stimulants– They are used in older pets in general so their use in CRF might be helpful. Periactin and Mirtazapine are common appetite stimulants.
Anabolic steroids– They are also used in older pets for arthritis and appetite stimulation with good success. They might help counteract the affects of anemia, although this can not be relied upon. DecaDurabolin is the one we use most frequently. Drugs like this are no longer readily available.
Calcitriol– It is postulated that some of the symptoms of CRF are the result of elevated levels of parathyroid hormone. This hormone helps in the regulation of calcium levels in the bloodstream. By adding low doses of the hormone calcitrol the parathyroid hormone will be suppressed, and your pet might feel better. The phosphorous level must be controlled, and the calcium level monitored closely, if one of our doctors decides to use this modality.
Azodyl- Azodyl is a patented formulation of naturally-occurring beneficial bacteria (Kibow Biotics®) that can be used to support renal health
Epakitin– Epakitin is a chitosan, calcium carbonate, lactose and hydrolyzed soy protein based nutritional supplement/food supplement.
At some select veterinary universities (University of Georgia) a new kidney can be transplanted into a cat. This does not cure the problem, it is a help in controlling the problem in cats that are losing weight and are anemic in spite of medical therapy. This specialized surgery can cost upwards of $10,000. Your cat has to be kept on immunosuppressive therapy (cyclosporine and prednisone) the rest of its life, and the donor cat has to be adopted. Complications can occur, especially rejection of the new kidney.
This is Skipper with his wonderful mom in for special testing before he goes to Georgia for his kidney transplant
Skipper returned several months later feeling much better and with his new brother!
Pets presented with renal disease, whether ARF or CRF, carry a guarded prognosis. It can be successfully controlled in most circumstances, especially if the diagnosis is made early enough. If your pet is hospitalized with CRF we will closely monitor its blood panel, paying special attention to BUN, creatinine, and phosphorous. If the excess levels of these tests decrease dramatically during hospitalization, and your pet improves clinically, then the use of medications and SQ. fluids at home are usually advantageous.
All pets that have been diagnosed with CRF should have a blood panel, a urinalysis, and physical exam performed every 3-6 months. This disease will progress, and other diseases might present themselves, so this type of monitoring is crucial for a good quality of life.