University of Tennessee Knoxville, TN back to the top Porto-Systemic Shunt WB Thomas DVM Dipl. A porto-systemic shunt is an abnormal communication between the portal blood system and the systemic circulation that allows blood from the intestines to enter the systemic circulation without first passing through the liver. This causes the body, including the brain, to be exposed to toxins originating in the intestines. Most porto-systemic shunts are congenital, that is, present at birth. In some cases, an acquired portosystemic shunt can develop secondary to an underlying liver disease.
Hepatic encephalopathy is a syndrome of abnormal brain function resulting from liver disease.
In dogs, hepatic encephalopathy is most commonly caused by a portosystemic shunt, but other liver diseases, such as liver tumors, cirrhosis, and congenital urea cycle enzyme deficiency can also cause hepatic encephalopathy. Congenital portosystemic shunts are most common in Miniature Schnauzers, Yorkshire terriers, Irish wolfhounds, Cairn terriers, and old English Sheepdog, but any breed can be affected. Signs and symptoms are usually present by 6 months of age, but congenital portosystemic shunts are occasionally not recognized until middle age. WB Thomas DVM Dipl. The brain requires sugar for normal function, and unlike many other organs, the brain has a very limited ability to store glucose.