A portosystemic shunt is an anomalous blood vessel that permits some of the intestinal blood to be diverted from its normal pattern (through the liver) and enter the general circulation.  Usually all gastrointestinal venous blood travels through the liver to be “de-toxified” before it gets to the heart and to the rest of the circulation.  Some of these toxins are formed by the bacteria in the intestine as a by-product of food breakdown.  When these toxins get into circulation without passing through the liver, they can create episodes of abnormal behavior, temporary blindness and seizures, and a variety of gastrointestinal problems.  Other signs can include repeat urinary tract infections, urinary bladder stones, increased thirst and urination, and low blood sugar.

Portosystemic shunts can be diagnosed by a series of tests.  Bile acid analysis is a good blood test for screening suspected cases.  Ultrasound of the abdomen, radionuclide scans and contrast radiographic (X-ray) study ot the intestinal (portal) circulation can be very useful in definitively identifying presence and location of portosystemic shunts.

Some shunts are not amenable to surgical correction for a variety of reasons .  These patients usually receive life-long treatment with a low protein diet and medications which alter the amount of toxins produced by the bacteria of the intestinal tract.  This treatment is not a cure, but is designed to minimize symptoms. Eventually, many animals with this problem will develop liver failure.

Patients who have the type of shunt that can be corrected with surgery have the best chance of being cured.  The surgery, however, is fraught with potential complications.  Generally, the older the patient is, the more risk of complications.  Some of the complications include post-operative infection, intestinal congestion related to portal hypertension, an inability of the liver to accommodate the increased blood flow, fluid in the abdomen, and seizures.  Severe complications can result in death.  The first two weeks after surgery is a critical time.  With a good recovery, the patient can be “cured” and usually goes on to live a normal life.