Portosystemic shunts are a type of vascular abnormality that causes blood to be emptied into the circulation, without passing through the liver.
[3] Symptoms of congenital PSS usually appear by six months of age[4] and include failure to gain weight, vomiting, and signs of hepatic encephalopathy (a condition where toxins normally removed by the liver accumulate in the blood and impair the function of brain cells) such as seizures, depression, tremors, drooling, and head pressing.
Urate bladder stones may form because of increased amounts of uric acid in circulation and excreted by the kidneys.
[6] Thus in the juvenile and adult animal with PSS, blood from the intestines only partly goes through the liver, and the rest mixes into general circulation.
Ultrasonography can also be used to estimate hepatic volume and vascularity, and to identify related lesions affecting other abdominal structures, such as urinary calculi.
Rectal portal scintigraphy using 99mtechnetium pertechnetate, a technique of imaging involving detection of gamma rays emitted by radionuclides absorbed through the rectum and into the bloodstream, demonstrates the blood vessel bypassing the liver.
[4] Methods of shunt attenuation should aim to slowly occlude the vessel over several weeks to months in order to avoid complications associated with portal hypertension.
These methods include ameroid ring constrictors, cellophane banding, intravascular or percutaneous silicone hydraulic occluders.
[12] Both methods have reportedly good outcomes in both cats and dogs, although the true composition of readily sourced cellophane has been found to be made from plastics (inert) and not cellulose (stimulates a fibrous reaction).