A crystalline acid, C₅H₄N₄O₃, occurring as an end product of purine metabolism. It is formed from purine bases derived from nucleic acids (DNA and RNA). It is a common constituent of urinary stones and gouty tophi.

Figure: URIC ACID CRYSTALS (×400)





OUTPUT
The uric acid output should be between 0.8 and 1 g/day if the patient is on an ordinary diet. Uric acid must be excreted because it cannot be metabolized.

Increased elimination is observed after ingestion of proteins and nitrogenous foods, after exercise, after administration of cytotoxic agents, and in gout and leukemia. Decreased elimination is observed in kidney failure, lead poisoning, and in people who eat a protein-free diet.

Subentries:
endogenous uric acid
exogenous uric acid