Dog Portosystemic Shunt — Welfare and Treatment

Portosystemic shunts — abnormal blood vessel connections that bypass the liver — cause neurological and systemic illness in affected dogs and require early diagnosis and treatment for welfare-positive outcomes.

Key Facts

A portosystemic shunt (PSS) is an abnormal vascular connection that allows blood from the gut to bypass the liver, causing toxin accumulation in the bloodstream
Congenital PSS occurs most frequently in Yorkshire Terriers, Maltese, Miniature Schnauzers, and Irish Wolfhounds
Clinical signs include stunted growth, neurological abnormalities (head pressing, circling, seizures), vomiting, and excessive thirst
Hepatic encephalopathy — brain dysfunction caused by ammonia accumulation — causes episodes of confusion, disorientation, and seizures
Diagnosis involves blood ammonia testing, bile acids pre- and post-meal, and imaging (ultrasound, CT, scintigraphy)
Surgical correction by ameroid constrictor or cellophane banding is curative in many dogs with extrahepatic shunts
Medical management (low protein diet, lactulose, antibiotics) can stabilise dogs awaiting surgery or in non-surgical cases

Welfare Considerations

Dogs with untreated PSS experience recurring episodes of hepatic encephalopathy — neurological events that are frightening and disorienting, involving involuntary movements, loss of orientation, and collapse. The chronic low-level toxin accumulation affects mood, cognition, and behaviour even between episodes. Without diagnosis, these dogs may be mismanaged as "difficult" or neurologically compromised animals without addressing the underlying cause. Early surgical correction offers curative outcomes for many dogs, with significantly improved quality of life — catching the condition early is the key welfare goal. Breed-specific awareness and routine screening blood tests in affected breeds help identify the condition before neurological damage becomes irreversible.

What You Can Do

If your dog is of a predisposed breed and shows stunted growth, neurological signs, or post-meal disorientation, request bile acid testing immediately
Seek referral to a specialist for surgical assessment if PSS is confirmed — surgery offers the best long-term welfare outcome for extrahepatic shunts
Feed a veterinary-recommended low-protein diet during medical stabilisation to reduce ammonia production
Administer lactulose and prescribed antibiotics consistently — these reduce ammonia absorption and improve quality of life
Work with your vet to recognise and manage hepatic encephalopathy episodes safely — emergency protocols reduce suffering during acute events
Support breeding programmes in predisposed breeds that screen for PSS and avoid breeding affected animals
Donate to veterinary hepatology research — surgical technique advances and medical management improvements directly benefit PSS welfare outcomes