RESEARCH ARTICLE Demonstration of natriuretic activity in urine of neurosurgical patients with renal salt wasting [version 1; referees: 2 approved]

We have utilized the persistent elevation of fractional excretion (FE) of urate,> 10%, to differentiate cerebral/renal salt wasting (RSW) from the syndrome of inappropriate antidiuretic hormone secretion (SIADH), in which a normalization of FEurate occurs after correction of hyponatremia. Previous studies suggest as well that an elevated FEurate with normonatremia, without pre-existing hyponatremia, is also consistent with RSW, including studies demonstrating induction of RSW in rats infused with plasma from normonatremic neurosurgical and Alzheimer’s disease patients. The present studies were designed to test whether precipitates from the urine of normonatremic neurosurgical patients, with either normal or elevated FEurate, and patients with SIADH, display natriuretic activity.: Ammonium sulfate precipitates from the urine of 6 RSW and 5Methods non-RSW Control patients were dialyzed (10 kDa cutoff) to remove the ammonium sulfate, lyophilized, and the reconstituted precipitate was tested for its effect on transcellular transport of Na across LLC-PK1 cells grown t