Figure 239

Mechanisms of extracellular fluid (ECF) volume expansion in nephrotic syndrome. Nephrotic syndrome is characterized by hypoalbuminemia, which shifts the relation between blood and interstitial volume upward (dashed to solid lines in inset). As discussed in Figure 2-35, these effects of hypoalbuminemia are evident when serum albumin concentrations decrease by more than half. In addition, however, hypoalbu-minemia may induce vasodilation and arterial hypotension that lead to sodium (Na) retention, independent of transudation of fluid into the interstitium [73,74]. Unlike other states of hypoproteinemia and vasodi-lation, however, nephrotic syndrome usually is associated with normotension or hypertension. Coupled with the observation made in Figure 2-36 that natriuresis may take place before increases in serum albumin concentration in patients with nephrotic syndrome, these data implicate an important role for primary renal Na retention in this disorder (dark blue arrow). As suggested by Figure 237, the decrease in urinary Na excretion may play a larger role in patients with acute glomerulonephritis than in patients with minimal change nephropathy [71].

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