Liver Shunt Screening for Puppies

Liver shunt, also known as portosystemic shunt, is a health condition that can occur in puppies as a form of congenital birth defect. Dogs and puppies affected by the condition have problems with the normal flow of blood from the digestive tract through the liver via the portal vein, but in dogs suffering from liver shunt, this healthy blood flow is either absent entirely or partially compromised.

Blood that has passed through the liver should then exit the liver along with venous blood to go back to the heart to be pumped again, but in puppies suffering from liver shunt, the blood bypasses the liver partially or entirely, and without the necessary blood flow to the liver, a range of health problems and a general failure to thrive will occur, which can ultimately prove fatal.

There are two different types of liver shunt in puppies, which are referred to as intrahepatic, in which the blood is redirected via a blood vessel within the liver itself, or extrahepatic, in which the blood that should pass through the liver is instead diverted via a blood vessel outside of the liver.

Whilst in utero, affected puppies will effectively have their blood passed through the liver of their dam, which means that the condition only becomes apparent after the pup is born and this can no longer occur.

A failure of blood to circulate through the liver in the normal way means that the liver cannot perform the various roles that are necessary in order to keep the puppy healthy, such as removing waste products from the bloodstream for elimination in waste. This causes a build-up of toxins and waste products in the pup’s bloodstream, which can pose an acute risk to the dog’s health and wellness.

Exactly how badly the condition affects any given dog can vary considerably from case to case; a low-level partial shunt may have little impact on the dog, whilst a total shunt can cause acute and serious health problems, which can prove fatal.

Because liver shunt in dogs is a congenital birth defect rather than caused by a gene mutation, it is not possible to perform DNA screening prior to breeding to identify the risk factors for any given dog-however, once born, dogs can be screened for the condition by other methods, in order to provide a complete picture of the dog’s health, and their potential viability for breeding.

In this article, we will look at liver shunt screening for puppies in more detail, including what sort of dogs are at risk for the condition, and how screening is carried out. Read on to learn more.

Why do puppies develop liver shunt?

Liver shunt is a congenital birth defect, which means that there is a hereditary element to the condition but that it is not caused by a specific gene mutation.

If either of the parent dogs were themselves affected by liver shunt to any degree, the chances of them passing it on to their offspring rise significantly. Even a dog with a very minor liver shunt can potentially produce a litter of puppies that are affected, in some cases to a much greater degree than their parent or parents.

What breeds are at risk?

Liver shunt has been identified as occurring with a sufficient degree of regularity as to be considered as posing a threat to the wider health of the breed and its gene pool as a whole within the Maltese dog breed, and of course any cross breed dogs with Maltese ancestry, such as the Maltipoo.

The condition can of course present in other breeds too, but the Maltese is the breed considered to be at the greatest risk of the condition.

What does screening involve?

If you own a Maltese or Maltipoo puppy that shows no signs of problems and that you don’t intend to use for breeding, screening for the condition is usually considered to be unnecessary. However, if a litter is born with symptoms of liver shunt, such as a failure to thrive, poor growth rate, vomiting, diarrhoea and other symptoms, it is important that the litter be screened as soon as possible, in order to get a definitive diagnosis.

Liver shunt can often be surgically corrected, in order to allow the affected pups to live a normal lifespan and enjoy a good quality of life. Additionally, if you own an adult Maltese dog that you wish to use for breeding, it is very wise to get them screened too.

Screening for liver shunt can be performed in a variety of different ways, and generally, if your vet suspects a problem of this type they will either refer you to a specialist referral clinic for further investigation, or screen the dog in-house and ask for a specialist to assist with interpreting the results.

Liver shunt screening can be performed by means of x-rays, ultrasound or radiographic intravenous liver dye, and a full laboratory blood work-up may be performed first to seek the markers of the condition and so, assist with diagnosis or the direction to take with screening.