Hepatic encephalopathy describes a spectrum of potentially reversible neuropsychiatric abnormalities seen in patients with liver dysfunction and/or portosystemic shunting. Overt hepatic encephalopathy develops in 30 to 45 percent of patients with cirrhosis and in 10 to 50 percent of patients with transjugular intrahepatic portal-systemic shunts [1,2]. The International Society for Hepatic Encephalopathy and Nitrogen Metabolism consensus defines the onset of disorientation or asterixis as the onset of overt hepatic encephalopathy . Some patients with hepatic encephalopathy have subtle findings that may only be detected using specialized tests, a condition known as minimal hepatic encephalopathy [4-6]. Minimal hepatic encephalopathy is seen in up to 80 percent of patients with cirrhosis [7-13].
Hepatic encephalopathy is often easy to detect in patients presenting with overt neuropsychiatric symptoms. It may be more difficult to detect in patients with chronic liver diseases who have mild signs of altered brain function, particularly if the underlying cause of the liver disease may be associated with neurologic manifestations (such as alcoholic liver disease or Wilson's disease).
This topic will review the clinical manifestations and diagnosis of hepatic encephalopathy in adults. The pathogenesis and treatment of hepatic encephalopathy are discussed elsewhere. (See "Hepatic encephalopathy: Pathogenesis" and "Hepatic encephalopathy in adults: Treatment".)
CATEGORIZATION AND GRADING
A generally accepted nomenclature for hepatic encephalopathy was proposed by the World Organization of Gastroenterology (OMGE) based on a consensus statement developed by a group of experts meeting at the 11th World Congress of Gastroenterology in Vienna in 1998 (table 1) . It takes into account both the type of hepatic abnormality and the duration/characteristics of the neurologic manifestations.
A classification scheme based on this nomenclature has been proposed (table 2) [14,15]: