Hepatic encephalopathy is characterized by accumulation of which substance in the bloodstream?

• A. Bilirubin
• B. Glucose
• C. Calcium
• D. Ammonia

Answer: (D)

Hepatic encephalopathy stems from the liver’s impaired ability to detoxify toxins that originate in the gut. The most important toxin involved is ammonia. Intestinal bacteria break down dietary protein into ammonia, which is normally converted to urea in the liver and then eliminated. When liver function is compromised or blood shunts around the liver, ammonia accumulates in the blood and can cross into the brain. There it is taken up by astrocytes and converted to glutamine, causing swelling of brain cells, altered neurotransmission, and cerebral edema. This leads to cognitive changes, confusion, mood alterations, sleep disturbances, and in more advanced cases, asterixis and coma. Bilirubin buildup causes jaundice but not the encephalopathy symptoms; glucose and calcium levels don’t define hepatic encephalopathy. So the substance accumulating in the bloodstream that characterizes hepatic encephalopathy is ammonia.