Pathogenesis of sodium and water retention in high-output and low-output cardiac failure, nephrotic syndrome, cirrhosis, and pregnancy (2).

This article has analyzed the pathogenesis of sodium and water retention in several circumstances. The initiator of retention has been proposed to be either a fall in cardiac output (e.g., low-output cardiac failure and vasoconstrictor hypovolemic nephrotic syndrome) or peripheral arterial vasodilatation (e.g., high-output cardiac failure, cirrhosis, arteriovenous fistula, and pregnancy). In the only state discussed, in which the kidney is diseased and not merely responding to extrarenal reflexes--i.e., nephrotic syndrome--intrarenal mechanisms may predominate and lead to expansion of the arterial vascular tree and suppression of the renin-angiotensin-aldosterone system (i.e., hypervolemic nephrotic syndrome). Otherwise, when kidneys are healthy, either a fall in cardiac output or peripheral arterial vasodilatation may diminish arterial vascular filling and thereby initiate a series of hemodynamic and hormonal events that result in renal sodium and water retention (Fig. 7). Finally, the approach presented in this article should be considered to be a vantage point from which to evaluate states of sodium and water retention, but not to be an exclusive position.