Proventricular Dilatation Syndrome (PDS)

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Proventricular Dilatation Syndrome (PDS) , also known as Macaw Wasting Disease (it was first seen in macaws), is a devastating disease of mostly young psittacines. The proventriculus is the chamber of the digestive tract just in front of the ventriculus (gizzard). When it dilates there is an inability of the stomach to digest food. It can be a problem in any psittacine, but is found most commonly in macaws and cockatoos.

Cause

A virus is the most likely cause.

Symptoms

Birds that have this problem are weak, have lost weight, and can have difficulty perching. Many of them will regurgitate and pass undigested seeds in their droppings.

Regurgitation of a mucous like fluid is one of the classic signs of PDS. There might be seeds adhered to the mouth and feathers around the face.

Diagnosis

Young cockatoos and macaws that have symptoms of this disease warrant further diagnostic tests. Other diseases can mimic PDS, so it is important to follow a thorough diagnostic process. Baby birds and those with infections, cancer or toxicities can also have a dilated proventriculus. Sometimes a biopsy of the crop or proventriculus is needed to confirm the diagnosis.

X-rays are a significant aid in making this diagnosis. The chambers of the stomach will show enlargement, which can be outlined with barium. Barium allows us to see the structures of the digestive tract more clearly. It also lets us know if the digestive tract is normal by assessing how long it takes for the barium to pass through to the end.

To understand how we perform a radiographic analysis of this problem it is important to understand the radiographic anatomy of a bird:

This is a normal x-ray of a bird laying on its right side. The head is towards the left. The diagram below explains the structures.

AS- air sac

PV- proventriculus

Vent- ventriculus (gizzard)

S- spleen

H- heart

This bird has PDS. The arrows circle the hugely dilated proventriculus.

We frequently give barium to help in outlining the digestive tract and to look for causes of the dilated proventriculus other than PDS.

In this x-ray the barium filled crop is on the far left (arrow on far left), there is barium in the esophagus (arrow in middle) and the ventriculus has barium in it (arrow on far right). The dilated proventriculus, without any barium in it, can be seen just to the left of the ventriculus.

Treatment

PDS carries a poor prognosis. Medication to minimize vomiting and supportive care with fluids, antibiotics, and feeding small amounts of food at each meal might be helpful temporarily.