Clinical and Interpretive

Ammonia levels are useful in assisting in the diagnosis of hepatic coma, investigating and monitoring treatment for inborn errors of metabolism, and evaluating patients with advanced liver disease.

Ammonia is a waste product of protein catabolism; it is potentially toxic to the central nervous system. Increased plasma ammonia may be indicative of hepatic encephalopathy, hepatic coma in terminal stages of liver cirrhosis, hepatic failure, acute and subacute liver necrosis, and Reye’s syndrome. Hyperammonemia may also be found with increasing dietary protein intake.

The major cause of hyperammonemia in infants includes inherited deficiencies of urea cycle enzymes, inherited metabolic disorders of organic acids and the dibasic amino acids lysine and ornithine, and severe liver disease.

Plasma ammonia concentrations do not correlate well with the degree of hepatic encephalopathy.