An Unusual Cause of Encephalopathy: Spontaneous Portosystemic Shunt

Abstract

Purpose: A 76-year-old male with no history of liver disease was evaluated for multiple episodes of confusion and altered mental status for two years. Patient was repeatedly found to have elevated ammonia levels during prior hospitalizations for altered mental status. He was on medical management of hyperammonemia with rifaximin and lactulose with little benefit. There was no history of alcohol abuse or recreational drug use. Vital signs and physical exam on presentation were normal, with no signs of chronic liver disease or asterixis. He was admitted with evidence of mild confusion. Labs on admission were notable for Ammonia: 83 and 112 μg/dl (two consecutive days); AST 110, ALT 110, Alkaline Phosphatase 151 (U/L). Total Bilirubin 0.7 mg/dl, INR 1.30. There was no evidence of HBV or HCV infection, iron overload or autoimmune liver disease. Head CT revealed age related cerebral atrophy. Abdomen CT showed no radiologic evidence for cirrhosis. Abdominal portography demonstrated multiple intrahepatic portosystemic shunts. An attempt at shunt embolization via a transjugular approach was unsuccessful. A transmesenteric approach was then used. The patient underwent minilaparotomy and placement of a blunt directional canula in the superior mesenteric vein. The major portal branch supplying the upper shunt was occluded with two vascular plugs and several embolization coils. The portal branch supplying the lower shunt was embolized with an IVC filter, followed by deployment of a vascular plug and several embolization coils within the filter. Smaller portal vein branches supplying the shunt were also selectively embolized. The patient's ammonia levels normalized after the procedure and he was asymptomatic during the rest of his hospital stay. Spontaneous large intra hepatic portosystemic shunts in the absence of chronic liver disease are extremely rare and are associated with persistent embryonic venous anastomoses. It is hypothesized that blood flow in the shunt increases with age. Progressive decreased tolerance to toxins like ammonia in the aging brain may explain the late presentation of these cases. Only the symptomatic cases need medical or surgical intervention. This is a rather unusual case of spontaneous, perhaps congenital extensive shunting that presented late in life with severe episodic hyperammonemia and confusion. Symptoms responded briskly to successful angiographic closure of the shunt.