Which laboratory finding is most consistent with hyperammonemia-related encephalopathy?

• A. Elevated serum glucose
• B. Elevated serum ammonia
• C. Elevated bilirubin
• D. Low albumin

Answer: (B)

Hyperammonemia causes encephalopathy by the brain’s exposure to ammonia, a toxic metabolite that is normally detoxified by the liver. When ammonia accumulates, it crosses the blood-brain barrier and is taken up by astrocytes, where it is converted to glutamine. This leads to astrocyte swelling, cerebral edema, and impaired neurotransmission, producing the cognitive and personality changes, confusion, or coma seen in hepatic encephalopathy. Therefore, the most consistent laboratory finding is an elevated serum ammonia level.

Other labs reflect liver injury or metabolic status but not the specific neurotoxic process. Elevated glucose can occur with illness but doesn’t indicate ammonia toxicity. Elevated bilirubin signals cholestasis or hepatocellular injury but doesn’t directly measure encephalopathy risk. Low albumin points to chronic liver dysfunction and reduced synthetic function, not the acute neurotoxic state.