A liver shunt in dogs is a blood vessel abnormality that allows blood from your dog’s intestines to bypass the liver and go straight to their heart. The condition affects around 1 in 1000 dogs and is usually a birth defect. Liver shunts can affect dogs of any sex or size, but are most common in small dogs and certain breeds.

Liver shunts let toxins and unprocessed nutrients from the gut flow all around the body. It’s as if the liver isn't working, so symptoms resemble those of liver disease. They vary in severity from mild to life-threatening. In the short term, symptoms can be managed with medicine and a special diet. But curing liver shunts requires complex surgery.

What are liver shunts in dogs?

Other names for liver shunts include portosystemic shunts or porto-caval shunts. Most liver shunts are diagnosed in dogs under 1 year old.

• 80% of liver shunts are congenital. This means they’re present at birth.

• 20% of liver shunts are acquired. These shunts happen in dogs with certain kinds of liver disease.

Liver shunts in dogs are blood vessels that bypass the liver. That’s fine when a puppy is in the womb. Their blood has been through their mum’s liver first. But when a puppy is born, the vessel should close. The pup starts to feed and its own liver gets to work. 

• The liver is the body’s processing plant.

• Blood from the intestines is full of ‘raw’ nutrients. The liver turns these into fuel for the body.

• Without help from the liver, most nutrients are unusable. And they can be very harmful. 

• Blood from the intestines will also carry toxins. 

• Lack of nutrition and the build-up of toxins make your dog very sick.

• A toxic chemical called ‘ammonia’ causes some of the most severe symptoms. It’s produced by bacteria in the intestine when they digest proteins. Increasing ammonia harms your dog’s entire body, especially their brain.

Shunt blood vessels can be outside the liver (extrahepatic) or inside the liver (intrahepatic). In both cases, shunted unfiltered blood gets past the liver.

• Congenital shunts happen because of a genetic (birth) defect. We don't always know why it happens. But it can be an inherited condition in Irish Wolfhounds.

• Acquired shunts result from severe and advanced liver disease. Dogs with acquired liver shunts will be very ill because of the underlying illness.

What are the symptoms of liver shunts in dogs?

Dogs with liver shunts show a wide range of symptoms.

These include:

• Poor body condition: failure to gain weight, stunted growth, and weight loss.

• Neurological symptoms: head-pressing, tiredness, depression, unsteadiness, walking in circles, blindness, and seizures.

• Gastrointestinal upsets: vomiting, diarrhoea, and not eating.

• Urinary changes: drinking more, urinating (peeing) more, difficulty passing urine, and bladder stones.

Symptoms may be present all the time, and they may worsen after your dog eats something.

Which dogs are at most risk of having a liver shunt?

 A number of factors affect how likely your dog is to have a liver shunt:

• Shunts outside the liver (extrahepatic shunts) are most common in small breeds of dogs, including Yorkshire terriers, West Highland terriers, Maltese terriers, Miniature Schnauzers, and Bichon Frise. 

• Shunts inside the liver (intrahepatic shunts) occur in larger breeds of dogs, including Irish Wolfhounds, Labradors, and Golden Retrievers.

• Liver shunts usually appear in puppies and young dogs less than a year old. But sometimes blood can flow through the liver as well as the shunt. In these cases, symptoms may be milder and show up later in older dogs.

How do vets diagnose liver shunts? 

Shunts are not always easy to diagnose. Especially partial shunts, where some blood from the gut does pass normally through the liver. This means your dog may still get enough nutrition and less severe or only intermittent toxic effects.

Aside from the symptoms, vets diagnose liver shunts from:

• General blood tests: to check organ health and red and white blood cells.

• Urine tests: to check for urate crystals and stones, which form in the urine when liver shunts develop.

• Special blood tests: for ammonia, and the bile acid stimulation test.

• Advanced imaging: including an ultrasound scan and a CT scan.

• Advanced imaging with ‘contrast studies’: using special dyes and imaging to ‘see’ how blood travels through the body. Sometimes surgery is carried out at the same time if the abnormal blood vessel is located.

How do vets treat liver shunts in dogs?

As soon as a vet suspects a liver shunt, they’ll start your dog on medical treatment to control the symptoms. But treatment for a liver shunt usually means a complicated operation to close the abnormal vessel. 

Medical treatment: aims to reduce ammonia production and ensure your dog gets enough energy.

• Special diet: provides essential nutrition, even for puppies. 

• Lactulose: a liquid medicine that stops bacteria from making ammonia.

• Antibiotics: to control gut bacteria.

• Anti-seizure medicines: to control neurological symptoms.

Around one-third of dogs with shunts can be managed with medical treatment alone. These are usually older dogs with ‘partial’ shunts and some normal blood flow through the liver.

Surgical treatment: involves closing off the abnormal blood vessel to allow blood flow through the liver. 

• It’s not safe to close a shunt completely. The liver needs time to develop and adjust to its new workload. So it’s partially closed to start with, then gradually seals over with time. This might mean another operation later on.

• Your dog has a general anaesthetic, so they sleep through the procedure.

• The vet uses a silk suture material or a special type of cellophane band to partially close the shunt.

• Shunts inside the liver that can't be reached by a surgeon can be sealed from inside the blood vessel. This uses a spring coil threaded into the shunt vessel. A blood clot forms on the coil and gradually seals the shunt.

What are the possible complications of surgery?

Surgery is successful 85% of the time for shunts present at or shortly after birth. 10% of cases will need further operation(s) or medical management. Around 5% of dogs will not recover from the operation.

Caring for a dog with a liver shunt at home

There are no home remedies for liver shunts. But good home care is an essential part of treating and managing liver shunts in dogs.

• Give all medicine prescribed by a vet at the correct time and dose.

• Ideally, feed a prescription diet to safely provide your dog with the nutrition they need. This is especially important for puppies and young growing dogs. 

• If a prescription diet isn’t an option for your adult dog, feed easily-digested proteins and avoid red meat. Eggs, soy and dairy protein are better options.

• For treats, stick to meat-free dog biscuits, non-toxic fruit and vegetables, or safe prescription treats.

• Always get advice from your vet before feeding home-cooked diets or treats to your dog.

Quality of life

Surgery isn’t suitable for every type of patient and every type of shunt. And sometimes surgery is not successful. Your dog may deteriorate in the days immediately after surgery, or continue to suffer from severe symptoms. Worsening seizures and neurological problems are particularly devastating. Medical treatment alone may not keep them comfortable and able to enjoy a happy life. If this happens, it may be kindest to allow your dog a peaceful escape with an overdose of anaesthetic (euthanasia). 

It’s a heart-wrenching decision to make at any time, and especially with a young dog. But all we can focus on is what’s best for them. Always talk to a vet for support.

Are other pets at risk?

Liver shunts affect individual dogs. Other dogs and pets are not at risk. 

Can liver shunts in dogs be prevented?

• Congenital liver shunts are present at birth and can't be prevented.

• A gene causing liver shunts has been identified in Irish Wolfhounds. Dogs with a liver shunt should not be used for breeding. Even if surgery ‘cured’ them! 

• Some acquired shunts can be prevented if the underlying liver disease is identified early and is treatable.

Liver shunts in dogs - when to worry   

Find your nearest emergency vet if your dog is:

• Suddenly blind

• Not responding to you

• Unconscious

• Looking weak, vacant or unsteady

• Having a fit or seizure

Joii can help with:

• Recognising the symptoms of a liver shunt

• Advice on medication to dogs

• Selecting the right diet

• Talking through concerns about illness and quality of life