Eradicate livershunts in dogs

Did you know that a healthy liver saves you from getting poisoned every single day? It filters your blood, removing toxins and other waste products along the way. And that’s exactly how it works in other mammals, too.

Except that it doesn’t in dogs with a congenital liver shunt. These dogs are born with an extra blood vessel, which guides the blood around the liver, rather than through it. This means that the blood doesn’t get filtered and toxins end up where they don’t belong – in the body. The result? A very sick dog.

The two genes that cause these liver shunts are thought to be the same for several breeds of small dogs: Cairn terriers, Yorkshire terriers, Jack Russell terriers, Miniature Schnauzers, Pugs and many more. If we could solve the problem in some of those breeds, many others would benefit as well.

The dangers of livershunts

A congenital 'extrahepatic portosystemic shunt' is a common problem in many dog ​​breeds. However, the most obvious question that arises is: what is an 'extrahepatic post-systemic shunt'? 

In a healthy animal (or human, for that matter), blood is transported through the stomach, the intestines and other internal organs, where it is infused with all sorts of substances, both useful (such as nutrients) and toxic. Prior to reaching major organs, such as the heart or the brain, the blood is pumped via the portal vein into the liver, where it is cleaned of most of the harmful substances. 

A post-systemic shunt is an additional, inborn blood vessel which connects the portal vein directly to one of the major veins leading to the heart, thereby bypassing the liver and preventing the blood from being cleaned.  Such a blood vessel can either be located inside (intrahepatic) or outside (extrahepatic) the liver. Intrahepatic shunts are most commonly seen in larger breeds such as the Irish Wolfhound, Bernese mountain dogs and Hovawarts. In smaller breeds, such as the Cairn terriers, extrahepatic shunts are diagnosed much more frequently. 

So why does this happen? 

Interestingly enough, the intrahepatic shunt starts out as an embryonal blood vessel. Throughout the development of the foetus, this embryonal vessel is responsible for direct transportation of oxygen and nutrion rich blood towards vital organs like the brain and the heart. In a healthy dog, this vessel is closed within the first few days of birth. However, in some, unfortunate cases, it remains open, and thus continues to exist as an intrahepatic shunt.

An extrahepatic shunt is an aberrant vessel which is formed during development of the fetus.

A small vein = a big problem

The clinical presentation of both the shunt types is identical: the majority of the blood pumped into the portal vein is directed towards the large vein outside the portal drainage area - rather than towards and through the liver. As a result the liver will cease to function properly. Blood is not filtered of toxic substances, which enter the body directly. 

One of the byproducts of protein degradation in the abdomen, ammonia, is considered particularly dangerous. As ammonia accumulates in the brain, it ends up causing very severe neurological symptoms. In essence, any animal with a hereditary shunt ends up slowly being poisoned. 

Until now, little is known about the cause of portosystemic shunts. In addition to the Cairn terrier, many other breeds are diagnosed regularly with shunts. However, experts do agree that heritable factors are responsible. Initial research shows that multiple genes are most likely involved, making the issue rather complex.

A future without liver shunts

Over the past few years we've made enormous progress in our search for the genetic background of extrahepatic portosystemic shunts. Using Cairn terriers as an example, we found a relation between the disease and two different genes. This same relation was confirmed in Yorkshire terriers, West Highland White terriers, Jack Russell terriers, Miniature Schnauzers en Shih Tzu proving an identical genetic cause.

We would now like to extend our research, in order to confirm these initial findings.

Help us

Your support will ensure that Dr. Frank van Steenbeek and his team can keep working towards developing a genetic test and assist breeders and breeding association in designing sustainable breeding strategies.   

Please help us today!