Schematic representation of the major sources of ammonia production and its excretory pathway (GI = gastrointestinal, IMV = inferior mesenteric vein). The key is that although hepatic causes (namely, the many causes of decompensated liver disease) are the most common, there are also many non-hepatic causes. They can be grouped into increased production of ammonia and decreased metabolism. = Non hepatic causes of hyperammonemia = Impaired elimination of ammonia: - Inherited Urea Cycle Disorders - Portosystemic shunts - Urinary diversion – ureterosigmoidostomy, ileal conduit - Medications - Valproic acid - Chemotherapy agents – 5FU, asparaginase Excess (production) of ammonia: - Urease producing UTI (i.e proteus) - Multiple myeloma, CML, AML - Large GI bleed - Significant endogenous dietary protein Other (rare): - Reye syndrome (Peds) - Primary carnitine deficiency #Ammonia #Pathophysiology #Hyperammonemia #Differential #Diagnosis
