Table 2.

Typical etiologies of nonhepatic hyperammonemia

Increased ammonia production	Decreased ammonia clearance
Infections by urea-producing bacteria: Proteus mirablis, Klebsiella species, Escherichia coli, Morganella morganii, Providencia rettgeri, diphtheroids, Mycobacterium genavense, herpes simplex	Ureterosigmoidostomy
Hematooncological disorders: multiple myeloma, chemotherapy for acute leukemia, bone marrow transplantation, 5-fluorouracil	Portosystemic shunts; congenital intrahepatic and extrahepatic
Organ transplantation	Drug-induced: valproic acid, glycine, carbamazepine, ribavirin, sulfadiazine with pyrimethamine, salicylate
Protein load and increased catabolism: severe exercise, seizures, starvation or trauma, total parenteral nutrition, gastrointestinal bleeding, steroid use	Inborn errors of metabolism: urea-cycle disorders, defects in β-oxidation of fatty acids, organic acidemias, disorders of pyruvate metabolism