Portosystemic Shunts in cats and dogs

Portosystemic Shunts in cats and dogs

Every now and again we are faced with a very unusual case. Last month we had a cat that presented having had a number of seizures. After a series of blood tests and scans it became clear that the cat had a congenital liver problem. Although liver disease might not be the first thing that you would expect to cause a cat to have a fit, we do see it when the liver is significantly reduced in function. One of the main jobs of the liver is to filter blood coming from the intestines, detoxifying and metabolising substances that have been absorbed into the blood supply. If the liver doesn't deal with these toxins, they can enter the brain and trigger seizures. Our poor cat had a 'liver shunt' which is essentially a blood vessel bypassing the liver circulation and preventing the liver from doing its job. Thanks to a detailed CT scan we could see the abnormal blood vessel leaving the intestines and entering the circulation near the left kidney, completely side-stepping the liver.

The challenge is what to do with the shunt. Tempting as it might be to simply ligate/tie off or remove the blood vessel, if we were to force all the circulating blood back through the liver, the cat's liver would be simply unable to cope with the sudden increase in blood flow. The solution is a gradual restriction of blood through the shunt over a period of weeks to months until the liver can build up its ability to cope with the increased blood supply.

The first surgical challenge was to identify the shunting vessel but thanks to our CT scan we were able to find it near the left kidney as expected. I then placed a special device called an 'ameroid constrictor' around the blood vessel. The constrictor looks like a tiny ring of metal with an inner lining of a material that can absorb moisture and gradually swell until the centre of the ring is completely occluded. Although the surgery was technically difficult, the cat recovered well and returned home the next day. He went on to make a full recovery.