Hepatic encephalopathy is a complex neuropsychiatric syndrome that may occur in such diverse clinical situations as inherited errors of the urea cycle, acute or chronic liver disease, and spontaneous or iatrogenic portosystemic venous shunting, including that following procedures to establish a transjugular intrahepatic portosystemic shunt. The clinical manifestations of this syndrome range from subtle abnormalities detectable only by psychometric testing to deep coma. Several grading systems have been proposed; one based on clinical and electroencephalographic abnormalities is shown in Table 1. 1 Hepatic encephalopathy may be present in 50 to 70 percent of all patients with cirrhosis, including those with abnormalities demonstrable . . .