Hepatic encephalopathy is caused by disorders affecting the liver. These include disorders that reduce liver function (such as cirrhosis or hepatitis) and conditions where blood circulation bypasses the liver. The exact cause of the disorder is unknown.
However, when the liver cannot properly metabolize and detoxify substances in the body, toxic substances build up in the bloodstream. One substance believed to be particularly toxic to the central nervous system is ammonia, which is produced by the body when proteins are digested, but is normally detoxified by the liver. Many other substances may also accumulate in the body and contribute to damage to the nervous system.
In people with otherwise stable liver disorders, hepatic encephalopathy may be triggered by episodes of gastrointestinal bleeding, excessive intake of dietary protein, electrolyte abnormalities (especially decrease in potassium, which may result from vomiting or treatments such as diuretics or paracentesis), infections, renal disease, and procedures that shunt blood past the liver.
The disorder may also be triggered by any condition that results in alkalosis (alkaline blood pH), low oxygen levels in the body, use of medications that suppress the central nervous system (such as barbiturates or benzodiazepine tranquilizers), surgery, and sometimes by co-occurring illness.
Disorders that mimic or mask symptoms of hepatic encephalopathy include alcohol intoxication, sedative overdose, complicated alcohol withdrawal, Wernicke-Korsakoff syndrome, subdural hematoma, meningitis, and metabolic abnormalities such as low blood glucose.
Hepatic encephalopathy may occur as an acute, potentially reversible disorder or as a chronic, progressive disorder associated with chronic liver disease.
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