My Pet has a Liver Shunt! Now What? What to Know About a Pet with a Liver Shunt

What is a liver shunt and who gets them?

Liver shunts, which are also called portosystemic shunts, are blood vessels that develop and take the blood, which would normally come from the intestines and go directly to the liver to be filtered and cleaned and will shunt or bypass the liver. This prevents the liver from performing some of the many important liver functions, breaking down nutrients in food, metabolizing medications, and eliminating waste products and toxins. Since the blood is no longer being filtered by the liver, toxins can start to build up in the blood system and potentially lead to significant health problems. While liver shunts in dogs are not that common, they can be a significant problem to the dogs that are either born with a shunt (congenital) or if they develop a shunt due to liver disease (acquired). Shunts are most common in smaller breeds such as the Yorkshire Terrier, Cairn Terrier, Miniature Schnauzer, and Maltese, but can also be seen in large breed dogs such as the Doberman Pinscher, Irish Wolfhound, and Labrador Retriever, and they are not commonly seen in cats.¹

Why is a liver shunt a problem? – clinical signs

The liver is an essential organ that is involved in many metabolic functions including protein, fat, and carbohydrate metabolism, vitamin and mineral metabolism and storage, as well as toxin and waste management. When the liver does not receive the full blood supply due to a shunt, it cannot perform all the jobs it is supposed to do to the best of its ability. Metabolic effects may be seen, such as dogs not growing as well due to the inability to fully extract all the nutrition from their food. More significant signs may be due to the buildup of toxins in the blood, as the liver can no longer clean the blood before it goes to the rest of the system. Pets with shunts have problems with protein metabolism, as the waste products from protein metabolism are toxic and require processing in the liver. Ammonia is one such waste product that can build up and lead to significant neurological signs called, ‘hepatic encephalopathy’. These neurologic signs can look like the animal is walking around drunk, very lethargic, spaciness (staring off into space), head pressing against the wall or pacing, or there can be other signs such as stunted growth, vomiting, diarrhea, unresponsiveness, or even seizures. Not all pets with liver shunts will develop severe neurologic signs, but those that do should be medically evaluated and managed with your regular veterinarian.

Urate stone formation can also occur in these dogs due to the buildup of some of the waste products that are unable to be detoxified by the liver and can create stones in the kidney or bladder and can require medical attention as well. Interestingly, although cats do not commonly get liver shunts, a unique clinical sign in cats is copper-colored irises and hypersalivation. So drooling kitties with copper eyes take care!

How do I know if my pet has a liver shunt? - diagnostics

Some pets with liver shunts will not have obvious signs and may only be found incidentally upon regular bloodwork monitoring, while other pets may have a congenital risk, or show severe signs that lead your veterinarian to run some diagnostics to confirm a liver shunt. Sometimes owners of new puppies will notice odd behavior after feeding, this is a definite time to talk to your vet.

Typically, a minimum database is collected to start.

• Complete blood count - can sometimes show that blood cells are not as big as they should be or that there is anemia (too few blood cells), which can be indicative of a liver shunt.
• Serum biochemistry - can show if the liver is functioning by measuring some of the essential proteins that the liver is responsible for making; in liver shunt patients these values are low – meaning the liver isn’t making these essential proteins.
  • also evaluates some of the enzymes that the various organs use and in liver patients’ liver enzymes are often higher showing increased activity.
• Urinalysis - can show if one of the potential consequences of liver shunts (urate stone formation) is potentially occurring by checking for the presence of urate crystals in the urine.

Further testing to confirm a liver shunt can include tests like a bile acid test, or doing some advanced imaging with ultrasound, or nuclear scintigraphy, both of which are tests that can help image the blood vessels. It is important to diagnose if blood is shunting past the liver and from where it is shunting, as shunts can be intrahepatic (from within the liver) or extrahepatic (outside the liver) and can help determine management or treatment options.

What do I do to manage my pet with a liver shunt?

The type of shunt intra- or extrahepatic can be part of the determining factor in how to manage a pet with a shunt. Some shunts can be corrected surgically, while others due to the location of the shunt, or the cost of the surgical procedure, must be managed medically. Even pets with shunts that can be fixed surgically, should be medically managed until the surgery has been performed and confirmed to be successful, as sometimes surgery is not completely successful or new shunts arise in response to the fixed one.

Think of it like congestion on the highway, if there is too much congestion, the body decides to create new exit ramps where there shouldn’t be ramps, and now all the stop lights, properly paved roads, etc. (the checks and balances of the liver filtering and doing its job) are not running as they should and its chaos and accidents everywhere!

When medically managing a pet with a liver shunt, there are a few tools that can help, and depending on the severity of the disease many pets with portosystemic shunts can live a happy life. None of the medical management options will correct the liver shunt, but rather aim to decrease the signs of the problem. One of the most important management steps is proper nutrition. The liver has many vital roles, and it needs all the nutrients in proper amounts to perform those functions. There are veterinary therapeutic diets that have been designed for dogs with liver disease including liver shunts, and they tend to be lower in protein than many typical commercial diets as they are aiming to provide enough protein for the liver to do its job, but no additional protein to reduce the possible toxic waste product build-up that occurs with protein digestion, which could lead to getting the dog sick. Often, feeding smaller meals more often is recommended, to help reduce the amount of protein being digested at each meal, thus reducing the potential buildup of toxins as well. It is important to carefully evaluate the food you feed and discuss with your veterinarian the best options for your pet. Growing animals have additional nutritional concerns, and some diets designed for the management of portosystemic shunts may not be appropriate for some dogs, particularly large breed puppies.² It is recommended to consult a Board Certified Veterinary Nutritionist^® found here, if your pet is not eating an appropriate diet as they can formulate an appropriate home-cooked diet that meets your individual pet’s needs and provide many other helpful insights into nutritional management of shunts.

When managing nutrition for a portosystemic shunt, both the amount of protein and the type of protein play an important role. Animal proteins, such as muscle meats and organ meats have been associated with poorer outcomes, and soy, egg, and dairy proteins can sometimes be fed in higher amounts without leading to negative signs of liver shunts.^3-5 Many veterinary therapeutic diets for a pet with a portosystemic shunt typically use vegetable, egg, or soy proteins, and may have moderate protein content, to provide the ‘goldilocks’ amount of protein – not too much to cause problems such as hepatic encephalopathy, but not too little to cause problems such as inadequate protein either. Problems of low protein can be seen in these pets as well, as some foods may not provide enough protein for the liver to do all its many jobs. When this happens, the body then turns inward to its muscle stores and can start to use that as a source of protein – leading to muscle loss and further poor health. Each pet with a liver shunt will be able to tolerate different amounts of protein, thus talking with your veterinarian about the best option for your pet or requesting a consultation with a Board Certified Veterinary Nutritionist^® is recommended. Ensuring that your pet is eating enough of a balanced appropriate meal is important, and it is important to remember that treats count as part of your pet’s food. Low protein treats such as non-toxic fruits and vegetables make great options, as these are also typically low-calorie and can help stay within the recommended 10% treat allowance to ensure the main diet isn’t becoming unbalanced. Other treats, such as animal crackers, breakfast cereals, or meatless dog treats are good options as well.

Lastly, some medications can help in the management of pets with liver shunts, and these include medications such as lactulose, to help move food through the system faster, creating less of a chance for toxin buildup (but also creating a softer, more frequent stool), or antibiotics to help alter the bacteria in the gut that can contribute to the toxic waste products which the liver would usually filter out. It is best to discuss with your veterinarian what treatment (if possible) or management options are best for your pet.

In conclusion, having a pet with a liver shunt means making some alterations to a typical pet's lifestyle. If your pet is diagnosed with a liver shunt, even if surgical correction is an option, discuss your pet's diet history (including treats, supplements, dental care treats, etc.) and determine if a more appropriate diet can be offered to help manage your pet either in the short term or over the course of their life.

References:

1. Tivers M. Liver: Vascular disorders. In E. J. Hall, D. A. Williams, & A. Kathrani, BSAVA Manual of Canine and Feline Gastroenterology, 3rd Ed. 2020;pp. 268-276. Gloucester: British Small Animal Veterinary Association.
2. Grant CE, Dodd S, Abood SK, & Verbrugghe A. Commercial diet recommendations and follow-up for a large breed puppy with an intrahepatic portosystemic shunt. Canadian Veterinary Journal, 2021;62:598-604.
3. Condon RE. Effect of dietary protein on symptoms and survival in dogs with an eck fistula. The American Journal of Surgery, 1971;107-114.
4. Proot S, Biourge V, Teske E, & Rothuizen J. Soy protein isolate versus meat-based low-protein diet for dogs with congenital portosystemic shunts. Journal of Veterinary Internal Medicine, 2009;23:794-800.
5. Marks SL. Nutritional Management of Hepatobiliary Diseases. In A. J. Fascetti, & S. J. Delaney, Applied Veterinary Clinical Nutrition 2012;pp. 235-250. West Sussex: Blackwell Publishing.

About the author: Dr. Sarah Wilson DVM DACVIM-Nutrition is a Board Certified Veterinary Nutritionist^® and is Director of Veterinary Nutrition within Nutrition Services at BSM Partners. She has practiced clinical veterinary medicine as well as specialized in Veterinary Nutrition. She enjoys working as a consultant on all things veterinary nutrition. In both a clinical setting for individual patients and as a consultant for the pet food industry, providing appropriate nutritional advice on a small scale (single patient) or a large scale (industry) allows Dr. Wilson to talk about her favorite things all day long: food and pets!

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