Portosystemic Shunt (PSS)
VP Client Information Sheets By VIN Community Contributors Portosystemic Shunt (PSS) Authored by: Becky Lundgren, DVM A portosystemic shunt (PSS, portasystemic shunt, portocaval shunt, portacaval shunt, liver shunt, hepatic shunt, or porto-systemic vascular anomaly) happens when a pet’s venous blood from the stomach, intestines, pancreas, and spleen bypasses the liver. The pet can be born with the shunt (congenital) or can get it later (acquired). About 80% of the cases are congenital, although sometimes a pet can have both types. About 25-33% of the congenital shunts are within the liver. Approximately 0.18% of all dogs have congenital shunting. During pregnancy, the portal blood vessel in the fetus bypasses the liver (the mother’s liver filters out toxins for the fetus). Normally this shunt closes within three days after birth. In affected animals, the shunt doesn't close and the blood continues to bypass the liver. Because the liver filters toxins, if it is bypassed the toxins build up in the body. This results in the puppy or kitten having slow or nonexistent growth (failure to thrive). If left untreated, puppies and kittens are not likely to survive. Congenital shunts seem to happen more in purebreds than in mixed breeds. Breeds with increased risk of PSS include Yorkshire terrier, Maltese terrier, Silky terrier, miniature schnauzer, miniature and toy poodles, Lhasa apso, Bichon Frise, shih tzu, Havanese, Dandie Dinmont terrier, Pekingese, German shepherd dog, golden retriever, Doberman pinscher, Labrador retriever, Irish setter, Samoyed, Old English sheepdog, Irish wolfhound, Australian shepherd, Australian cattle dog, Himalayan, and Persian. No sex predisposition has been documented.
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