Two calves and two foals presented with episodic clinical signs of diffuse central nervous system disease. Portosystemic anomalies were tentatively diagnosed based on the history, clinical signs, and increased serum concentrations of blood ammonia and total serum bile acids with normal concentrations of liver derived enzymes. One calf died before intraoperative contrast portography, whereas the other calf and both foals had marked clinical improvement after intensive medical therapy. Surgical correction was attempted in these three animals and was successful in one foal. A right paracostal celiotomy was superior to a ventral median approach for exposure to the portal vascular system and shunt access.