Clinical and pathophysiological effects of piretanide treatment in the nephrotic syndrome

12 patients with the nephrotic syndrome (N.S.) and normal serum creatinine (less than 1.5 mg/dl) were investigated in a follow-up study over 10 days under diuretic treatment with piretanide (29 +/- 24 pg/ml). Clinical effects, parameters of renal clearance and hemodynamics, metabolic changes and the influence on vasoactive and volume dependent hormonal systems were studied. Piretanide markedly increased urine volume and electrolyte excretion (Vu +53%, UNa +24%, p less than 0.05, after 10 days treatment) but did not significantly alter glomerular filtration rate or renal blood flow. While baseline plasma renin activity was in the normal range and regularly stimulated (2.55 ng/ml x h to 7.7 ng/ml x h) plasma ANP values were elevated (152 +/- 107 pg/ml) at the start of the study and did not significantly change under piretanide treatment. This may be an indicator of sodium retention and a high plasma volume in the primary form of the nephrotic syndrome. Thereby piretanide did not significantly alter the intravascular space.