Congenital portosystemic shunts (CPSS) are hepatic vascular anomalies which can affect any breed ofdog or cat. Extrahepatic CPSS are most commonly observed in cats and small dogs, whereas intrahepaticCPSS are more likely to affect large breed dogs. A hereditary basis has been observed in some dog breeds.Affected animals are usually presented at young age with a variety of neurological, gastrointestinal, urinaryor other signs. Signs of hepatic encephalopathy often predominate. The pathogenesis of this condition isnot yet completely understood and is probably multifactorial. The underlying cause is probably the influenceon the brain of one or more toxins which normally speaking should be detoxified by the liver. Ptyalismis a very common sign in cats with CPSS.