What Causes Liver Shunt in Dogs and Cats? How Liver Diseases Can Affect Your Pet

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A liver shunt is caused when blood flow bypasses the liver entirely. Find out what causes liver shunts in dogs and cats and what you can do to help your pet.

Portosystemic shunt (PSS), more commonly known as liver shunt, is a condition in which the circulatory system bypasses the liver, denying fresh blood flow to this vital organ. Liver shunt is more often found in dogs, but cats are also susceptible to this condition. Read more about the causes and symptoms of liver shunt in dogs and cats.

What Is Liver Shunt?

Liver shunt occurs when there is an abnormal connection between the liver and the hepatic portal vein. The liver typically receives 75 percent of its blood supply from this blood vessel. The vessel’s primary function is to bring rich nutrients to the liver, which then processes them and rids them of toxins.

Causes of Liver Shunt in Dogs and Cats

Liver shunt is either present at birth (a congenital portosystemic shunt) or it develops later in life (an acquired portosystemic shunt).

Acquired liver shunt most often develops due to liver disease, such as cirrhosis. In the case of cirrhosis, pets experience portal hypertension, or high blood pressure in the hepatic portal vein.

Congenital liver shunt is a birth defect that forms in utero. The shunt appears either inside (intrahepatic) or outside the liver (extrahepatic).

  • Intrahepatic Liver Shunt: During gestation, a puppy or kitten’s liver is not functional. Instead, all detoxification comes from the mother’s liver for the entire litter. Intrahepatic liver shunt occurs when the fetal shunt (called the ductus venosus) that carries blood from the fetal liver to the heart does not seal.

  • Extrahepatic Liver Shunt: In this type of liver shunt, the ductus venosus seals properly at birth, but a blood vessel outside the liver develops abnormally, compromising blood flow. While intrahepatic liver shunts are solitary, multiple extrahepatic liver shunts can appear.

Breeds Most Susceptible to Liver Shunt

Cats more often develop extrahepatic liver shunts, with mixed breeds, Persians, British Shorthairs, Siamese, and Himalayans being some of the most common breeds with this condition. Small dogs are also more prone to develop extrahepatic shunts. Those canine breeds include:

  • Cairn Terriers
  • Dachshunds
  • Jack Russell Terriers
  • Lhasa Apsos
  • Maltese
  • Poodles
  • Shih Tzus
  • Yorkshire Terriers

Large dogs are more likely to develop intrahepatic shunts. Common breeds include:

  • Australian Cattle Dogs
  • Australian Shepherds
  • Labrador Retrievers
  • Old English Sheepdogs
  • Samoyeds

Symptoms of Liver Shunt in Dogs and Cats

Symptoms of congenital liver shunt may show up by the time your pet reaches six to twelve months in age.

Common signs of liver shunt in dogs and cats include:

If liver shunt is congenital, then pet owners may notice symptoms manifesting in a puppy or kitten’s development, such as stunted growth, low muscle mass, or trouble gaining weight.

Treatment and Prevention of Liver Shunt

Treating liver shunt could mean surgery, diet change, antibiotics, or the administering of supplements like Denamarin. Learn more about prevention and treatment.

More on Liver Problems

Denamarin for Dogs and Cats: Managing Liver Disease
Food for Liver Disease in Dogs and Cats
Liver Cancer in Dogs and Cats

This information is for informational purposes only and is not meant as a substitute for the professional advice of, or diagnosis or treatment by, your veterinarian with respect to your pet. It has, however, been verified by a licensed veterinarian for accuracy.

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