Familial Bartter's syndrome--a study of free water clearance.

Three siblings in one family were found to have Bartter's syndrome. All of them had persistent hypokalemia, metabolic alkalosis, hyperreninemia and normal blood pressure. Patient 1 also had hyponatremia and hyperaldosteronism. Free water clearance studies during a maximal water diuresis showed that all of them had mild decrease in distal fractional chloride reabsorption. Patient 1 had normal proximal sodium reabsorption, however, patient 2 and patient 3 had enhanced proximal sodium reabsorption. These data suggest that the defect in chloride reabsorption at the Henle's loop may contribute to the pathogenesis of Bartter's syndrome, and compensatory proximal sodium reabsorption is very important in maintaining normal plasma sodium in Bartter's syndrome.