The physiology of uric acid and the impact of end‐stage kidney disease and dialysis

Uric acid‐mediated biological effects are milieu dependent. In a physiological milieu, serum uric acid serves as an antioxidant; when homeostasis is perturbed, divergent effects are observed depending on the clinical context. Several epidemiologic studies indicated the presence of a direct relationship between higher concentrations of serum uric acid and cardiovascular mortality; yet not all studies support this conclusion. Although high serum levels of uric acid are associated with higher mortality in patients with nondialysis‐dependent chronic kidney disease and perhaps in those with end‐stage kidney disease receiving peritoneal dialysis, the opposite relationship is seen in patients with end‐stage kidney disease on hemodialysis. This review discusses the pathologic mechanisms associated with elevated serum uric acid levels by clinical context; examines the interplay between uric acid metabolism and modality of renal replacement therapy; and presents hypotheses to rationalize the disparate associations between incremental levels of serum uric acid and survival across the continuum of kidney disease and by type of renal replacement therapy.