REN and Hyponatremia: We intend to briefly discuss the pathophysiology of RSW and SIADH, current methods of differentiating SIADH from RSW, the failure of the volume approach to address hyponatremia which has resulted in misconceptions and mismanagement of many hyponatremic patients, present data to support our proposal to change CSW to RSW, and removing reset osmostat (RO) as a subtype of SIADH, and present an algorithm which eliminates the need to assess volume, determine urine sodium concentration (UNa), plasma renin, aldosterone or atrial/brain natriuretic peptide (A/BNP).