Disorders of ECF Volume: Nephrotic Syndrome
Unlike patients with congestive heart failure (CHF) and cirrhosis, patients with nephrotic syndrome have some underlying renal disease. Also, effective circulating volume (ECV) is not decreased in all patients with nephrotic syndrome. This syndrome is characterized by proteinuria in excess of 3.5 g/day, hypoalbuminemia, hyperlipidemia, edema, and lipiduria. The mechanism for salt and water retention is not clear. The traditional (“underfill”) theory implies that loss of protein in the urine causes hypoalbuminemia and decreased plasma oncotic pressure. These factors favor fluid movement into the interstitium, resulting in intravascular hypovolemia and activation of salt-retaining mechanisms. Two lines of evidence, however, argue against this traditional theory. First, not all patients with congenital deficiency of albumin (analbuminemia) develop edema. Second, some patients with nephrotic syndrome have either normal or increased intravascular volume despite hypoalbuminemia. This evidence suggests that mechanisms other than hypoalbuminemia and decreased intravascular volume play a role in renal retention of Na+ in nephrotic syndrome.
KeywordsNephrotic syndrome Renal disease Hypoalbuminemia Hyperlipidemia Edema Lipiduria Electrolytes and nephrotic syndrome
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