Introduction
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.
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