Clinical signs and radiographic diagnosis of a portosystemic shunt in a foal.

A three-month-old native pony foal had a history of recurrent episodes of bizarre neurological behaviour. The results of clinical examinations were non-specific but clinicopathological investigations indicated hepatic encephalopathy. A percutaneous, needle liver biopsy revealed histopathological changes consistent with a portosystemic shunt, which was later identified by operative mesenteric portovenography, and confirmed at post mortem.