Canine Anine Portosystemic Shunt Symptoms and Treatments

A portosystemic shunt is an extra pathway between the hepatic venous system and the arterial circulation which needs to have shut down immediately after birth. In the uterus, the foetus is fed via the mother's umbilical vein which leads to the left side of the heart, completely opposite to the normal circulatory route which would mean the venous blood went to the right side of the heart and thence to the lungs to be oxygenated.

To correct this difference, a shunt opens up in the foetus to bypass blood from the left side of the heart into the arterial system. When this shunt does not automatically shut down after birth, the blood supply to the liver is compromised and this leads to poor or non-existent development of the liver.

In young dogs the compromised blood flow will result in abnormal neurological patterns, and failure to thrive in comparison to their siblings. However that is not to say that its siblings won't have the same condition, when it may simply be one or other of the siblings has a shunt that isn't completely closed off.

Diagnosis is confirmed by blood test and liver function tests, which will show compromised liver function, and is also dependent upon behaviour patterning. Depending on the results it is possible to offer surgery to some dogs if they are healthy enough for surgery and the liver is strong enough, and although the surgery is tricky, because success depends on the tension it is possible to close or partly close the shunt with a ligature which will give the dog an extra lease of life. The surgeon will partly close the shunt if the liver has not gained sufficient strength to cope with normal arterial flow, and he will need to take extreme care in ensuring that the partially occluded shunt is wide enough to let arterial blood through and yet narrow enough to avoid damaging the liver with a pressure it's not yet ready for.

Angiography is another possible diagnostic tool, and involves slipping an X-ray opaque tiny-bored catheter into the circulatory system by the shunt to determine its path and patency. Using image intensifier X rays the catheter can be moved and be seen in screen so that the surgeon can see where the occlusions are and where the shunt is.

Where surgery is not performed. in most cases the dog may be able to function properly with only part of a liver but the demands put on it as the dog develops are too much and he will most probably die at around 2 or 3 years old.

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