Health Articles

Liver Shunt: AKA Portosystemic Shunt

by Anne Jones RN, BSNE

This will not be the first time you have read in BFCA Health Times about portosystemic shunt. It is time to revisit the topic and to more closely examine health records to see if there are signs that it exists in Bichons Ė possibly even in your line. This is not an idea any breeder wants to address but it must be looked at objectively and now is a good time to do so. The Health Committee is making plans now to conduct another member/breeder health survey. While you are looking through records on your dogs, be aware of some of the following information. Consider carefully whether shunt may have been present in one or more of your dogs. This is not a letter of condemnation of your breeding plans; it is rather a light that could shine on past events that would make you a better breeder in the future.

The liver serves a number of functions, including cell breakdown, production of bile, storage of glycogen and fats, and filtration of toxins. Blood is transported through the body by an arteriovenous system of vessels that are called arteries and veins. Blood enters the liver to be filtered (cleansed) and filtered blood leaves the liver to travel again through the body. Bacteria, many chemicals, drugs and other substances (such as nutritional byproducts) are filtered there. This amazing organ has a huge effect on general health. A liver that functions properly is a basic component of good health. A liver that is unhealthy continues its work but not as efficiently. Human liver transplantation is done by a living donor with the patient receiving only a portion of that donor liver. The remaining portion is able to still function successfully in the donorís body. A healthy liver is amazing; an unhealthy liver makes every effort to maintain life.

Now read some of the signs of liver disease: seizures, stunted growth, brain dysfunction, blindness, jaundice, lethargy, inability to handle drugs and anesthesia, weight loss, rage episodes, circling and other strange habitual movements, urinary calculi, and many other seemingly unrelated events. Makes you wonder, doesnít it?

The possibility of portosystemic shunt (portal caval shunt is another name) has been discussed before but we continue to receive few reports unless it is diagnosed in a young puppy that does not thrive and dies within days or weeks of birth. Many dogs with shunt live for a number of years before effects begin to cause odd behaviors, seizures, and severe illness. Acquired shunts are those that open up later in life due to stress on the organ during disease or injury.

In large breeds, shunts are more often found inside the liver (intrahepatic). In small breeds the shunt is usually exahepatic shunt, occurring as small side branches of the portal vein outside the liver. This is the vein that is supposed to carry blood directly to the liver for cleansing but a shunt causes blood to be diverted around the liver. Therefore that blood is never filtered and toxins continue to circulate throughout the body. It is those toxins that are responsible for symptoms described in the earlier paragraph. By the way, shunt is a disease of purebred dogs.

All indications are that this is a genetic trait and it has already been identified as a major health problem in some breeds. Among breeds known to have heritable shunt are some that are close cousins to the Bichon Frise, having common ancestry. Are we lucky enough to have missed genes that other breeds now find so troublesome? While shunt may sometimes be a developmental problem, we can no longer afford to ignore it as a concern in our breed when we see a lot of liver related illness!

A term that may be new to you is Hepatic Microvascular Dysplasia. The condition is considered to be rare and is associated with milder symptoms than the traditional shunt described above. It is probably a hereditary developmental condition similar to that discussed earlier and is recognized in some breeds as such. As Bichon breeders, we do not want to find it any more than we want the previously known anomaly! If you have had a dog diagnosed with HMD, we urgently request that you send your data to the health committee.

There are tests that can be used to diagnose portosystemic shunt and surgery that can repair or treatment that can aid the affected dog. In a dog with a lesser degree of shunt, the symptoms may not appear for several years until there is major assault on the liver because of disease. It is probably a good idea to have testing done to eliminate liver function as a cause of serious signs that were indicated in a previous paragraph, especially in a dog having seizures. Blood chemistry, liver enzyme levels, low blood sugar, low serum cholesterol, the testing of bile acid levels, blood ammonia concentrations are all tests that may be mentioned by your veterinarian. Imaging by radiography or ultrasound, especially Doppler ultrasound, may be recommended. Doppler is probably best for diagnosing small extrahepatic shunt. Contrast dye may be needed to trace the blood flow. In the case of microvascular disease, liver biopsy may be necessary to reveal atrophy or small or absent portal vessels.

Once diagnosed, surgery will be one option. Without surgical correction, treatment will be aimed at managing symptomatically with antibiotics, dietary changes, control of urinary tract disease, if present, metabolic symptoms and control of neurotoxins. Protein restrictive diets, dietary additives and detoxification of ammonia will be a part of dietary management. The condition is a serious one, even in those dogs who did not present symptoms in the first weeks of life. Indeed as the dog ages, liver disease will complicate recovery of any other systemic health issue since detoxification is not occurring.

Every dog owner needs to be aware of symptoms and to be prepared to deal with a very sick dog if a malfunctioning liver is involved. Watch for those signs and discuss with your veterinarian whether surgical intervention is possible. Certainly other maintenance measures will be needed. And please report any disease to the health committee to enable us to better maintain our data.

Liver Cleansing Diet
For a diet that is useful for dogs with liver disease, those on extended medical treatment and dogs with epilepsy or seizures, the following link will provide a healthy home cooked diet. Please discuss this diet with your veterinarian before using it. It is a balanced meal designed by Dr. Jean Dodds and has been used by committee members for several years as a supplemental diet during illness. It is approved by The Epilepsy Foundation and others.
For more detailed information about liver disease go to