Abstract
Hepatic encephalopathy is uncommon in the absence of cirrhosis. We report a 71-year-old woman who presented with altered mental status in the setting of hyperammonemia for the second time in 6 months. Magnetic resonance imaging of the abdomen revealed an uncommon portosystemic shunt involving an enlarged posterior branch of the right portal vein and an accessory right hepatic vein, with no features of cirrhosis. Appropriate management of these patients with ammonia-lowering therapy can reduce repeat episodes and improve quality of life. This case demonstrates the importance of diagnosing non-cirrhotic hepatic encephalopathy in patients with altered mental status.