In railroad tracks and electrical circuits, shunts are useful things, allowing train cars or the flow of current to be diverted from one pathway to another. But a portosystemic shunt, which allows blood to flow abnormally around instead of to the liver, is a serious health problem in pets. Both dogs and cats can have portosystemic shunts, although it is much more common in dogs. Normally, the blood carries toxins and toxic by-products of metabolism from the stomach and intestines to the liver, where the toxins are removed. Congenital shunts are generally diagnosed in animals less than one year old.
Acquired shunts can occur at any age and are often caused by liver disease.
Congenital shunts are most commonly seen in small breed dogs, such as Yorkshire terriers or toy poodles. This disease can also affect large breed dogs. Unfortunately, larger dogs typically get intrahepatic shunts, which are much more difficult to treat. Dogs with congenital shunts tend to be small for their age and breed. Other signs of shunts include excessive drinking, frequent urination, and a condition known as hepatic encephalopathy.