Updated September 25, 2026. Fact-checked against veterinary sources; review by a licensed veterinarian is in progress. See our editorial policy.
Quick answer: A liver shunt (portosystemic shunt) is an abnormal blood vessel that lets blood bypass the liver, so toxins aren’t filtered properly. Most are congenital. Small breeds like Yorkshire Terriers, Maltese, Havanese, Pugs, and Miniature Schnauzers usually have shunts outside the liver, while large breeds more often have them inside it. Signs include poor growth, neurological signs after meals, and urinary stones. Many dogs do well after surgery.
Signs
- Small size or poor growth
- Confusion, circling, head pressing, blindness, or seizures, often after meals
- Drooling (especially in cats with shunts)
- Vomiting, diarrhea, or poor appetite
- Increased thirst and urination
- Urate bladder stones
- Slow recovery from anesthesia
Diagnosis
- Bloodwork, including bile acids and ammonia
- Urinalysis for urate crystals
- Ultrasound, CT, or other imaging
Treatment
- Medical management first: a moderate-protein liver diet, lactulose, and sometimes antibiotics to reduce toxins
- Surgery: devices like an ameroid constrictor or cellophane band gradually close the shunt
- Some dogs are managed long term with medication
Outlook
Many dogs with single shunts outside the liver have good outcomes after surgery. Your vet or a surgical specialist can discuss your dog’s specific case.
More: causes of liver disease in dogs.
Sources
- Merck Veterinary Manual: Portosystemic shunts
- American College of Veterinary Surgeons (ACVS): Portosystemic shunts
- Webster CRL, et al. ACVIM consensus statement on the diagnosis and treatment of chronic hepatitis in dogs. J Vet Intern Med. 2019
This article is for general education and is not a substitute for care from your own veterinarian. Learn about The Pet Vet and our editorial policy.