Hepatic encephalopathy is a complication of cirrhosis of the liver and its resultant portal hypertension, toxic substances accumulate in the blood and impair the function of brain cells. Signs can include impaired cognition, a flapping tremor (asterixis), and a decreased level of consciousness.

Pathogenesis

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Cirrhosis will obstruct the passage of blood through the liver causing portal hypertension. This means it is difficult for blood from the intestines to go through the liver to get back to the heart. Portal-systemic anastamoses ("shunts") develop, and portal blood (from the intestinal veins) will bypass the liver and return to the heart via another route without undergoing first-pass detoxification by the liver. Furthermore, the liver (damaged from the cirrhosis) will not be functioning as well as it should be, so blood that does travel through the liver may not be as detoxified as it otherwise would be.

The toxic substances involved are not well understood, but have been thought to include ammonia (NH₃) and mercaptans. Ammonia is normally converted to urea by the liver and, as with mercaptans, is produced by the bacterial breakdown of protein in the intestines.

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