Medical & Surgical Urology
Open Access

Abstract

Failure of Volume Assessment as a Diagnostic Approach to Hyponatremia:A New Algorithm

John K Maesaka, Louis J Imbriano, James Drakakis, Shayan Shirazian and Sairah Sharif

It is evident from recent advances in the evaluation and treatment of hyponatremia that the volume assessment as the first diagnostic step to delineate the cause of hyponatremia has failed. It is agreed that the clinical approach to determining whether a patient is euvolemic or hypovolemic has failed, especially differentiating syndromes of inappropriate secretion of antidiuretic hormone (SIADH) from renal salt wasting (RSW), syndromes with diametrically opposing therapy. The recommendation to treat virtually all hyponatremics creates an urgent need to differentiate SIADH from RSW. We intend to discuss the following: 1. contrary to popular opinion, RSW is much more common than SIADH, 2. the term RSW should replace cerebral salt wasting, 3. the clinical utility of determining fractional excretion (FE) of urate in hyponatremic conditions, 4. A normal FEurate can identify hyponatremic patients with reset osmostat (RO), 5. Propose eliminating RO as subtype of SIADH because of pathophysiologic differences, 6. the presence of a natriuretic factor in blood and urine of patients with RSW that may evolve into a biomarker for RSW, thus allowing differentiation of SIADH from RSW on first encounter and delivery of proper therapy, and 7. To propose a new algorithm to assess patients with hyponatremia.