Hepatic encephalopathy is a worsening of brain function that occurs when the liver is no longer able to remove toxic substances in the blood.

Hepatic encephalopathy is caused by disorders that affect the liver. These include disorders that reduce liver function (such as cirrhosis or hepatitis) and conditions in which blood circulation does not enter the liver. The exact cause of hepatic encephalopathy is unknown.

An important job of the liver is to change toxic substances that are either made by the body or taken into the body (such as medicines) and make them harmless. However, when the liver is damaged, these "poisons" may build up in the bloodstream.

Ammonia, which is produced by the body when proteins are digested, is one of the harmful substances that is normally made harmless by the liver. Many other substances may also build up in the body if the liver is not working well. They can cause damage to the nervous system.

Hepatic encephalopathy may occur suddenly in people who previously had no liver problems when damage occurs to the liver. More often, the condition is seen in people with chronic liver disease.

Hepatic encephalopathy may be triggered by:

• Dehydration
• Eating too much protein
• Electrolyte abnormalities (especially a decrease in potassium) from vomiting, or from treatments such as paracentesis or taking diuretics ("water pills")
• Bleeding from the intestines, stomach, or esophagus
• Infections
• Kidney problems
• Low oxygen levels in the body
• Shunt placement or complications (See: Transjugular intrahepatic portosystemic shunt )
• Surgery
• Use of medications that suppress the central nervous system (such as barbiturates or benzodiazepine tranquilizers)

Disorders that can mimic or mask symptoms of hepatic encephalopathy include:

• Alcohol intoxication
• Complicated alcohol withdrawal
• Meningitis
• Metabolic abnormalities such as low blood glucose
• Sedative overdose
• Subdural hematoma (bleeding under the skull)
• Wernicke-Korsakoff syndrome

Hepatic encephalopathy may occur as an acute, potentially reversible disorder. Or it may occur as a chronic, progressive disorder that is associated with chronic liver disease.