Pet Health Library

Liver Shunt in Dogs

Background

A liver shunt, also called a portosystemic shunt, is an abnormal blood vessel that shortcuts or “shunts” blood around the liver instead of following a normal pathway through the liver. The liver is vital in removing toxins from the blood, and when the liver is bypassed, toxins and waste  continue to circulate throughout the body causing clinical signs.

There are two categories of shunts, extrahepatic (outside the liver) and intrahepatic (inside the liver). While most portosystemic shunts are congenital (present from birth) in some circumstances, portosystemic shunts may develop as a result of another problem with the liver (acquired shunt). In dogs with congenital shunts, signs often appear at a young age.

Risk Factors

Liver shunts occur most often in the following breeds:

  • Havanese
  • Maltese
  • Norwich terriers
  • Pugs
  • Yorkshire terriers

Signs

Signs of a liver shunt include:

  • Failure to grow and thrive
  • Nervous system disturbances, including stumbling, seizures, and head pressing

However, some dogs may be asymptomatic.

Diagnosis

In a dog with signs of a liver shunt, a complete blood count, liver enzyme analysis, and a bile acid test are the starting points for diagnosis. Dogs with shunts are commonly anemic, have elevated liver enzymes, and extreme elevation in bile acids. A urinalysis is also regularly performed because the urine of dogs with liver shunts may contain ammonium biurate crystals. In some dogs, urate bladder stones occur. An abdominal ultrasound may be able to identify a shunt, but the preferred diagnostic procedure is an angiogram, which allows veterinarians to see an animal’s blood vessels. This procedure can identify the location of the shunt and determine whether it is a single shunt or if there are multiple shunts. It also allows veterinary surgeons to assess whether surgical correction is possible.

Treatment

Diet is an important component of managing liver shunts. Clinical signs may be significantly improved when dogs are fed a low-protein diet.  Several commercially prepared diets are available for dogs with liver conditions. Your veterinarian will recommend the best diet for your dog.

Surgical treatment of a shunt involves blocking blood flow through the shunting vessel. This may be done either by placing constrictors (metal loops) around the vessels or by placing a coil inside the shunting vessel to prevent blood flow.

If surgery is not an option, medications and a low-protein diet may help to manage the signs.

Prevention

Since liver shunts are congenital conditions, no preventive measures can be taken.

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