ABSTRACT
This chapter describes the following: the normal response to sodium depletion; clinical characteristics and laboratory findings; classification; and the sodium depletion states and their treatment. Sodium depletion results in cardiovascular, renal, and to some limited extent in other extrarenal homeostatic efforts to sustain the circulation, minimize additional losses, and restore volume. The gastrointestinal sodium losses are the major route of extrarenal exit of sodium from the body and constitute the single, most common cause of sodium depletion in practice. Solute diuresis is the most common cause of extrinsic renal sodium wasting. Mild sodium deficiency, on the other hand, results only in small but significant decreases in renal hemodynamics. The second form or overt variety, sometimes named salt-losing nephropathy, is usually clinically apparent and manifests itself as severe sodium depletion. A review of the daily volume and salt content of the body fluids involved underlines the predominance of the gastrointestinal tract as a major cause of sodium depletion.
