Possible discrimination of Gitelman's syndrome from Bartter's syndrome by renal clearance study: report of two cases.

We observed two patients who had hypokalemic metabolic alkalosis as well as hypomagnesemia and hypocalciuria with elevated serum renin levels. In renal clearance studies in our patients using furosemide or thiazide, urine volume and chloride clearance (CCI) were increased after furosemide administration but not after thiazide administration. Furthermore, the distal fractional chloride reabsorption [CH2O/(CH2O + CCI)] was dramatically decreased by furosemide administration in our patients, whereas thiazide had little effect on it, suggesting the presence of a defect in the distal tubule rather than in the thick ascending loop of Henle. These findings are compatible with the concept of Gitelman's syndrome, a variant form of Bartter's syndrome.