A 69-year-old man admitted because of a chief complaint of disturbed consciousness. Slightly decreased liver function, elevated ammonia blood levels, retention of ICG in serum at 15 minutes, and slight atrophy of the liver on CT scans were suggestive of the diagnosis of hepatic encephalopathy. Left renal venography demonstrated splenorenal-gastrorenal shunt. The histologic examination of the liver showed hemosiderosis. However, there was no liver cirrhosis or fibrosis that caused an appreciable portal hypertension. A shunt occlusion test using a baloon catheter was performed and ammonia levels and portal pressure values were measured before and after occlusion. The ammonia tolerance test following occlusion of the shunt showed no increase in ammonia level and a slight elevation of portal pressure. These results revealed that the portal blood entered the systemic circulation through the shunt. Portal-systemic encephalopathy without associated liver cirrhosis and fibrosis that cause prominent portal hypertension, as in this case, is rare. In this case, there was a past history of abdominal surgery and adhesion formed postoperatively appeared to be involved in the development of the shunt.