Hemodynamic and hormonal factors were monitored in nine patients with nephrotic syndrome who were evaluated relative to their capacity to excrete a 20-mL/kg water load (normal greater than 80%). In five "nonexcretor" patients (37% of water load excreted in five hours), as compared to four normal excretors (105% of water load excreted in five hours; P less than .01 v nonexcretors), neither BP (131/88 v 119/79 mm Hg), pulse (74 v 77 beats/min), cardiac index (3.7 v 3.1 L/min/m2), pulmonary wedge pressure (9.3 v 7.3 mm Hg), systemic vascular resistance (1537 v 1254 dynes-sec-cm-5), nor plasma volume (41.3 v 40.1 mL/kg) were different. Similarly, plasma renin activity (2.6 v 3.7 ng/mL/h), plasma aldosterone (12 v 10.9 ng/dL), and plasma norepinephrine (403 v 312 pg/mL) were not different between nonexcretor v excretor patients with nephrotic syndrome. Plasma vasopressin concentrations were also similar both before (3.1 +/- 0.8 v 2.4 +/- 1.2 pg/mL) and during the water load (0.9 +/- 0.3 v 1.0 +/- 0.4 pg/mL). Inulin clearances, however, were lower in the nonexcretor v the excretor nephrotic patients (37 v 78 mL/min/1.73 m2; P less than .02) and correlated with water excretion (r = .68; P less than .05). Head-out water immersion increased sodium (40 to 110 microEq/min; P less than .01) and water excretion (37% to 82%; P less than .025) in the nonexcretors; the improvement correlated with the increase in inulin clearance during immersion (r = .70; P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)