The following information on this page was taken from Dr. Karen Tobias, DVM, MS, Diplomate ACVS. Dr. Tobias' Email -

What is a Liver Shunt?
A Liver Shunt is a blood vessel that carries blood around the liver, instead of through it. In some animals a liver shunt is a birth defect, known as "congenital portosystemic shunt". In others, there are multiple small shunts, known as "acquired porotsystemic shunts", and they form because of severe liver disease such as cirrhosis.
Toxins, especially ammonia, build up in the blood stream and the dog has seizures due to increased ammonia levels. The liver is usually smaller than normal and will have decreased liver function. Secondary liver infection can occur but this plays a minimal role in the liver shunt syndrome. It is the bypassing of the blood thru the liver that is the major problem.
The symptoms of liver shunt can start to appear at almost any age. Dogs with a liver shunt are usually very thin dogs that pick at food. They not only have a poor appetite but they can become lethargic, dizzy, and stagger. They may try to climb out of their pen, climb higher on you, and cry and throw their head far back after eating, and they may go into convulsions.

Many breeders feel that it is an inherited disease and that the only way to eliminate that disease is to cull those dogs that are affected and producing this disease from their breeding program. SO FAR, IT HAS NOT BEEN PROVEN THAT THIS IS INDEED A HEREDITARY DISEASE, but it will probably be proven with the DNA studies that are being done right now. If a puppy has a test score that says it is free of liver shunt, it will never develop the hereditary type, but ANY YORKIE can develop an acquired liver shunt due to poor diet, high protein diet, stress, and other factors.

There are studies being done at this very moment, and they are on the verge of finding the DNA marker that will be able to test both sire and dam BEFORE they are bred, and this should go a long way in terminating this horrible disease.

Many toy breeds are affected, but yorkies, in the United States, have almost a 36 times greater risk of developing shunts than all other breeds combined!

The other breeds where liver shunt is a problem are: Low Chen, Schnauzers, Cairn Terriers, Maltese, Dachshunds, Cocker Spaniels, Jack Russel Terriers, Shih-Tzu, Lhasa-Apso, and Poodles.

Liver shunt Acquired vs. Congenital
Acquired shunts can form with severe liver disease or other conditions that cause high blood pressure in the liver. Shunts usually connect the portal vein, which normally carries blood from the intestines to the liver, to the caudal vena cava, which carries blood from the legs and kidneys to the heart. If blood pressure in the portal vein gets too high- maybe from scar tissue or severe swelling in the liver- shunts will form to carry the blood somewhere else. If there was a toxin in the food that caused severe liver swelling and scar tissue formation, then that could cause shunts to form. However, most dogs are very sick with the liver disease before they form acquired shunts and most continue to have health problems afterwards.
In other words, if their liver is so damaged that they form shunts (like people with alcoholism and cirrhosis), it usually remains damaged. Some shunts may get smaller as the liver swelling goes down. Many veterinarians only guess that a shunt is there based on blood work changes. We have seen several older dogs that have congenital shunts that are fine unless they get another illness; then the problem of the shunt shows up. Once the other illness resolves, the shunt may not cause noticeable problems (at least, the owners may not detect them).

There is a big debate as to whether liver shunts are hereditary. A disease is likely to be hereditary if it occurs more commonly in one breed than others, if it occurs in a family of dogs, or if it or a closely related disease is proven hereditary in other breeds or species.

To date, liver shunts are considered to be hereditary in Irish Wolfhounds, Cocker Spaniels, Maltese, and Yorkshire Terriers, and are probably hereditary in several other breeds. The affected dog should be castrated or spayed and, because of the mode of inheritance is not known, it is best to avoid breeding the parents of the affected dog.

Do all dogs with shunts have high bile acid results?
Dogs with shunts will almost always have high bile acids 2 hours after eating, and at least 95% of dogs will have high bile acids after a 12 hours fast. For the most accurate test results, samples are taken after a 12 hour fast, and then repeated 2 hours after feeding. This is done for several reasons. Some dogs normally release bile acids in the middle of the night, and therefore would have a higher fasting result. Other dogs may have fat in their blood after eating, which could interfere with the results. If only one sample can be obtained, it is best to take it 2 hours after feeding.

Do all dogs with high bile acids have shunts?
Bile acids can be increased with any liver disease. Bile acids can also be mildly increased in normal dogs, particularly in some breeds (such as the Maltese) where chemicals that naturally occur in their blood interfere with the test. Most dogs with liver shunts have after feeding results of well over 100 (normal is 15-20). If the bile acids are only slightly increased, the vet may want to re run the test in 3 to 4 weeks.

This disease usually goes hand in hand with a kidney disorder and it seems that a special diet can sometimes keep it under control with some dogs for a time. Surgery sometimes works depending on where the "shunt" is, and how large it is. Ameroid constrictor surgery is now being done on some LS victims, with a very high success rate. If your dog has been diagnosed with high bile acids, I would advise you to contact Dr. Karen Tobias for a referral.

For more information on this subject, please refer to:

Dr. Karen Tobias, DVM, MS, Diplomate ACVS
Professor, Small Animal Surgery
University of Tennessee College of Veterinary Medicine
Regent, American College of Veterinary Surgeons
President, Society of Veterinary Soft Tissue Surgery
University of Tennessee College of Veterinary Medicine

University Phone (865)974-8387
FAX (865) 974-5554
Dr. Tobias' Email -

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