Max was presented to the Feline Centre earlier this year when he was only eight months old. He had always had a poor appetite and had suffered occasional bouts of vomiting and diarrhoea. More recently his owners had noticed several episodes of strange behaviour during which he would display shivering, drooling of saliva, increased vocalisation and aggression. There had been no known access to toxins and the behaviour did not appear to be related to exercise or feeding.

Clinical examination was largely unremarkable but he was rather small for his age and his coat was in poor condition. Blood samples submitted for routine haematology (analysis of the blood cells) were unremarkable. Serum biochemistry (analysis of substances within the blood) revealed reduction in the levels of protein and urea. These changes can be seen in cats with liver problems although other problems can also result in low protein levels. An enzyme released from damaged liver cells (ALT) was also mildly elevated, though this can be noted in many non-hepatic diseases as well as in cats with liver disease.

Max's young age and clinical signs were suggestive of him having a portosystemic shunt. The most commonly seen signs are poor growth, drooling of saliva and neurological signs including odd behaviour. Max was showing all of these signs along with occasional gastrointestinal upsets, which can also be a feature of this disease.

A portosystemic shunt is a congenital defect in which an abnormal blood vessel shunts blood from the intestines straight into the general circulation, bypassing the liver. In a normal animal blood returning from the intestines is processed and detoxified in the liver before being passed to the rest of the body. In a patient with a portosystemic shunt the blood is not detoxified and this can cause clinical signs such as those seen in Max. The liver tissue is unable to function properly due to the reduced blood supply.

Tests

The most commonly employed test of liver function is the serum bile acid assay. Max's bile acid levels were found to be markedly elevated as were levels of the toxin ammonia, which is usually converted to urea by the liver. Imaging techniques can often be helpful in establishing a diagnosis of a portosystemic shunt. The liver can sometimes be noted to be small in size on X-ray and a large shunting blood vessel may be visualised using ultrasonography. Unfortunately this was not the case in Max and he required a special X-ray contrast study (portovenography). In this technique the liver is visualised directly via surgery and a contrast dye is injected into one of the intestinal veins. The dye can then be followed using fluoroscopy (real time X-rays) and any shunting vessels identified. Max was found to have a single abnormal shunting vessel which is by far the most common finding in cats with this condition. Treatment was by surgical ligation of the vessel to occlude its blood flow. Once the vessel had been tied off, blood from the intestines could be seen entering the liver in a normal way.

Max's treatment

After surgery Max made a good recovery and within a few weeks was back to being a bright, happy kitten. Since his operation he has had no further episodes of odd behaviour, his appetite has improved dramatically and he has gained weight. The most critical time is the few days following surgery, so the long term outlook for Max is now very favourable. In a small percentage of cats the condition can recur. This happens when the original shunting vessel is able to recanalise or where ongoing liver disease leads to the development of multiple new shunting vessels.