Regulation of renal urate excretion: A critical review

Uric acid metabolism is reviewed as it relates mainly to kidney and electro lyte disorders, with emphasis on the difficulties in understanding urate tr ansport because of its bidirectional transport and the species differences in which animal data may not have relevance to the human condition. A criti cal review of the effects of pyrazinamide and extracellular volume expansio n on urate transport raises questions about the current popular teachings t hat pyrazinamide exclusively blocks tubule urate secretion and extracellula r volume expansion has a major role in controlling urate excretion. There a ppears to be a renal salt-wasting syndrome with overlapping clinical featur es that make it indistinguishable from the syndrome of Inappropriate secret ion of antidiuretic hormone (SIADH), except possibly for extracellular Volu me depletion. Hypouricemia and the elevation in the fractional excretion of urate (%E/F-urate) are extensively reviewed with a proposal to use the per sistence of hypouricemia and elevated %E/F-urate after the correction of hy ponatremia to differentiate these patients from those with SIADH. An algori thm is proposed to differentiate one group from the other. A plasma natriur etic factor has been shown in some with probable renal salt wasting, which includes patients with AIDS, cancer, and pulmonary and intracranial disease s. The natriuretic factor may have etiologic implications and diagnostic an d therapeutic applications. (C) 1998 by the National Kidney Foundation, Inc .