Congenital extrahepatic portosystemic shunt with progressive myelopathy and encephalopathy.

Portosystemic encephalopathy commonly occurs in patients with portal hypertension caused by end-stage liver disease or portal vein thrombosis. Congenital extrahepatic portosystemic shunt (CEPS) is an underdiagnosed and treatable condition that can cause encephalopathy and various neuropsychiatric symptoms. We report an unusual case of type 2 CEPS in a 29-year-old woman who presented with progressive myelopathy and fluctuating encephalopathy on a background of congenital cardiac disease. Investigations showed hyperammonaemia, and despite no evidence of portal hypertension on ultrasound imaging, CT scan of abdomen showed a shunt between the mesenteric and left internal iliac veins. Patients with unexplained fluctuating or progressive neuropsychiatric symptoms should have their serum ammonia checked. A raised serum ammonia concentration without known portal hypertension should prompt further investigations for extrahepatic shunts.