The liver is an essential organ in a dog’s or cat’s anatomy. It plays a critical role in metabolism, digestion, detoxification, and the synthesis of essential proteins. In total, the liver performs over five hundred functions in the body. When this organ faces malfunction or disease, the implications can be far-reaching, affecting numerous bodily processes. Portosystemic shunts (PSS), also known as liver shunts, are one such malfunction. They are mostly congenital and occur more in dogs than in cats.
What is a liver shunt?
A liver shunt is considered an anatomical malfunction. It is an abnormal blood vessel that bypasses or “shunts” blood around the liver, thereby decreasing the flow of blood in the portal artery. The portal artery carries blood from the intestines to the liver for detoxification. Think of a garden hose taking blood through the liver instead of a branching tree with blood flowing throughout the liver tissue. When one or more liver shunts redirect blood away from the liver, toxins and waste continue to circulate throughout the body. This results in one or more systems in the body being negatively affected.
Liver shunts are mostly congenital and most often occur in young dogs and cats around one year of age. These puppies or kittens are often the “runt” of the litter or the “quiet” littermate. Some animals may not show signs of this congenital defect until later in life when the liver can no longer cope with abnormal blood flow. Purebred dogs and cats are more often affected; the most common dog breeds are Yorkies, Schnauzers, Bernese Mountain dogs, Huskies, Wolfhounds, Golden Retrievers, Labrador Retrievers, and Shepherds. Cat breeds include Persians, British Shorthair, Siamese, and Himalayan. Liver shunts are categorized according to their location.
- Extrahepatic portosystemic shunts (EHPSS) are congenital, form outside the liver and are the most common type. About 75% of liver shunts are extrahepatic.
- Intrahepatic portosystemic shunts (IHPSS) are diagnosed as a portal branch located inside the liver. These shunts are also considered congenital; about 20% of liver shunts are intrahepatic.
- Hepatic Arteriovenous Malformations (HAVMs) occur when the high-pressure hepatic artery is directly connected to the low-pressure system of veins inside the liver. This results in higher-than-normal blood pressure in the portal system of the liver. As a result of the high blood pressure, other shunts can develop and are considered “acquired.”
Acquired liver shunts are rare - about 2% of shunts are not congenital. Acquired liver shunts point to other problems that led to its development such as thrombosis (blood clots blocking the blood vessels), liver disease, and unusual anatomy.
What are the symptoms of a liver shunt?
There are three main systems that tend to be affected by liver shunts:
- Neurologic symptoms such as hyperactivity, restlessness, lethargy, apparent blindness, incoordination, hepatic encephalopathy, stupor, coma and seizures can occur when toxins and bacteria are not eliminated by a compromised liver. Some pets will "head press" against a wall.
- Gastrointestinal symptoms such as vomiting, diarrhea, loss of appetite and weight loss, and ascites (accumulation of fluid in the abdomen) occur because of poor liver perfusion (blood flow).
- Urologic symptoms such as excessive drinking and urinating, and creation of urate crystals and bladder stones are a result of the kidneys working overtime to detox the body when the liver is not working at its full capacity.
- Other liver symptoms such as jaundice can also appear because of a liver shunt.
How is a liver shunt diagnosed?
- A physical exam may show signs of jaundice and palpation of the liver will uncover abnormally small size. Stunted growth, poor muscle development, and neurological problems can also be identified with a physical exam.
- Blood work such as a CBC (complete blood count) and chemistry panel provide insights into the liver’s function. Decreased levels of BUN, total protein, albumin, cholesterol, and glucose may be seen on laboratory testing. Specific tests like ALT (Alanine Aminotransferase) and ALP (Alkaline Phosphatase) as well as bilirubin levels can indicate liver dysfunction.
- A urinalysis can detect the presence of bilirubin or urobilinogen, poor concentration of urine and kidney/bladder infections, as well as the presence of urate crystals or stones.
- A bile acids test measures the liver’s ability to process bile which aids in digestion. Elevated acid levels after a meal can suggest impaired liver function.
- X-rays (radiographs) can provide a visual of the liver’s size and shape. A smaller sized liver or “plump” kidneys may be seen.
- Since x-rays are relatively insensitive for shunts, ultrasound offers a more detailed view of the liver’s internal structure, detecting tumors, cysts, or changes in liver tissue.
- A Computed Tomography (CT) scan is the most expensive option and requires general anesthesia but gives the most definitive and detailed look into liver function. It is recommended to get a second reading and report of an ultrasound or CT scan as the findings are “operator dependent.”
What is the treatment for a liver shunt?
The treatment protocol selected by your veterinarian will depend on whether the shunt is congenital or acquired, its location (inside or outside the liver), and the severity of symptoms. If neurological symptoms such as seizures, lethargy, or hyperactivity are severe, medication may be used to stabilize the patient. Once stable, lactulose, a carbohydrate that serves as a laxative, is used to help the intestines eliminate toxins quickly before they can be absorbed into the system. Antibiotics are used to kill bacteria in the bowel so that waste products are unable to convert to ammonia. Appetite stimulants may also be indicated.
Surgical removal of the shunt is often the choice of veterinarians when a single extrahepatic shunt exists. Studies show that in general, surgical therapy in addition to medical management has a better prognosis and longer expected life. Surgeons use an Ameroid constrictor to stop the flow of blood from the shunt. Depending on the location, surgeons can also stop blood flow to an intrahepatic liver shunt. As with all surgery, there is a risk of complications including seizures, portal artery hypertension (high blood pressure), additional shunt formation, liver dysfunction, excessive bleeding, and taking too long to recover from anesthesia.
A specialized diet is often recommended to lower the levels of nitrogen (purine) in the system so that fewer toxins need to be eliminated. I do not recommend the use of commercial “prescription” low-protein diets for treatment of liver shunts. The diet should consist of high-quality, highly digestible proteins. To prevent urate crystals and stones, feed low and medium purine foods such as kale, broccoli, eggs, muscle meat from chicken, turkey, lamb, pork, beef, oats, and fruits. Avoid high-purine foods including organs (brain, heart, liver, kidneys), game meat, goose, nutritional yeast, mackerel, herring, sardines, mussels, scallops, spinach, cauliflower, mushrooms, and legumes (peas, beans, lentils, chickpeas). Recipes for adult dogs with liver shunt can be found in my book, Keeping Your Pet Naturally Healthy.
Since liver shunts prevent the liver from working in its fullest capacity, supplementation to support and detoxify the liver is recommended.
- Glutathione is a powerful antioxidant. It detoxifies the body, helps build DNA, and helps regenerate other antioxidants such as vitamins E and C.
- NAC (N-acetyl-cysteine) and SAMe help boost glutathione production and remove toxins from the liver.
- Herbs such as dandelion root, milk thistle, and turmeric also detoxify the body and are anti-inflammatory.
- CBD oil (cannabidiol) is anti-inflammatory, protects the liver, and lowers the seizure threshold for animals suffering from seizures.
It is essential to avoid as many toxins in your pet’s food, water, and environment as possible. Use cleaning products that are chemical-free and contain natural ingredients. Ensure clean, filtered water. Avoid flea & tick prevention chemicals of any kind. Do not use herbicides, pesticides, and rodenticides on your property. Toxins in food include pesticides and aflatoxins (mold toxins found in grains in pet food). Ultra-processed pet food, filled with preservatives and synthetic vitamin/mineral mixes, are highly inflammatory and place unnecessary stress on the liver.
Most liver shunts are considered relatively straightforward and treatable, and most cases have good outcomes. However, never hesitate to get a second opinion. The liver is a vital organ with an impressive capacity for healing. Supporting liver function by providing clean food, water, and an environment with as few toxins as possible will go a long way in supporting a pet with a liver shunt diagnosis.
