Uric Acid, 24-Hour Urine

Uric Acid, 24-Hour Urine (urine uric acid) evaluates uric acid metabolism and quantifies hyperuricosuria in patients with suspected or confirmed nephrolithiasis. The excretion profile helps differentiate uric acid overproduction states—including primary gout and secondary hyperuricemia—from other mechanisms, supports assessment for inherited or acquired defects of purine metabolism, and informs management of gout and stone prevention strategies. Uric acid stone disease is also seen in individuals with inflammatory bowel disease and after jejunoileal bypass; most patients who form uric acid stones do not have gout.

Uric acid arises from turnover of endogenous cells and ingestion of dietary purines. Most is eliminated in urine, with a smaller proportion excreted in stool. Uric acid filtered from the bloodstream undergoes renal tubular handling before final urinary excretion. Excess production raises the urinary uric acid concentration, whereas impaired renal handling may lower excretion. Sustained overproduction or underexcretion disturbs urinary concentrations and can predispose to stone formation and gout-related complications. Persistent hyperuricosuria promotes uric acid crystallization and nephrolithiasis. Hyperuricemia leads to deposition of monosodium urate crystals in joints and periarticular tissues, causing gout; without treatment, tophus formation may occur.