What is a Liver Shunt in dogs
A portosystemic shunt, or a liver shunt, is where an abnormal blood vessel carrying blood from the intestines bypasses the liver and enters the general circulation. The liver should remove all the toxins from the intestine, and if the liver is bypassed, these toxins reach the general circulation.
Liver shunts can be divided into two categories: those that are present at birth (congenital shunts) and those that develop later in life (acquired shunts). Congenital shunts are most common, being responsible for approximately 80 percent of cases. Dogs are usually quite young (less than 3 years old) when they start experiencing symptoms. Small/toy breeds especially Yorkshire and Cairn Terriers are predisposed. Acquired shunts typically develop when blood pressure within the veins connecting the digestive tract to the liver becomes elevated. Dogs with acquired liver shunts tend to experience symptoms when they are older in comparison to those diagnosed with congenital shunts.
Written by Dr. Mariella Roberts, Veterinary Surgeon, Animal Trust Vets CIC | Published February 2025 | Review date February 2027 | This advice is for UK pets only
Symptoms of portosystemic shunt in dogs
Dogs with liver shunts generally have some combination of the following symptoms:
Poor growth (congenital shunts)
Reduced eating and/or eating unusual things
Weight loss
Increased thirst and urination
Difficulty in passing urine or blood in the urine due to the formation of bladder stones
Vomiting, which may contain blood
Diarrhea, which may contain blood
Behavioural changes like mental dullness, staring vacantly, poor vision, unsteadiness, circling
When to contact your vet
When any symptoms above are evident or any concern you may have.
Diagnosis
A routine blood and liver function tests (bile acid stimulation test) are performed. Analysis of urine and culture will identify any bladder stones. An ultrasound or CT scan will identify the abnormal blood vessel. A special dye or contrast agent is injected into one of the veins to highlight the abnormal blood vessel.
Treatment: Medical Management & Surgical Treatment
Portosystemic shunts can be treated medically or surgically. Medical treatment is almost always recommended a few weeks before surgery to help make these patients safer for anesthesia and surgery. While medical management can help to control some of the symptoms of portosystemic shunting, it is widely considered that surgical management provides better long-term control and quality of life.
Medical management for portosystemic shunt in dogs:
Medical management for liver shunts can be used to improve a dog’s condition before surgery, when surgery is not in a dog’s best interest, or when surgery is unable to entirely correct the problem.
The goal is to reduce the amount of proteins in the diet and feed only on high quality, highly digestible protein diets.
Antibiotics are prescribed to reduce the number of bacteria in the gut.
Laxative is given to increase quick transit of stool through the guts to reduce the toxins.
Surgical treatment for portosystemic shunt in dogs:
Some patients are better suited for surgery, depending on factors such as how many blood vessels are affected, where the blood vessels are located and whether the disease has been caused by another condition. Surgery for liver shunts focuses on blocking the flow of blood through the abnormal vessels so that more of it travels through the liver.
Most small breed dogs who have congenital shunts have just one abnormal blood vessel that is located outside of the liver, best suited for surgical correction.
A single shunt that is located within the liver itself is more common in large breed dogs, again best treated with surgery, but the procedure is a little more difficult.
Dogs with acquired shunts tend to have multiple, abnormal vessels and may be poorer candidates for surgery due to an underlying illness.
Prevention
Unfortunately prevention is almost impossible but could be helped by not breeding pets if they are at risk of, or know to be affected by a liver shunt.
Outlook
The outcome is excellent in the majority of cases. Surgery provides the best chance for a long, healthy life in most dogs with extrahepatic shunts. Many dogs are clinically normal within four to eight weeks following surgery.