INCOMPLETE RENAL TUBULAR ACIDOSIS - PHYSIOLOGIC STUDIES IN 3 PATIENTS WITH A DEFECT IN LOWERING URINE PH

A defect in ability to lower urine pH in response to ammonium chloride loading in the absence of systemic acidosis is defined as the syndrome of incomplete renal tubular acidosis. Three patients are described who had recurrent nephrolithiasis in association with incomplete renal tubular acidosis. Two of these had hypercalciuria, one of whom had nephrocalcinosis. The third patient had nephrocalcinosis without hypercalciuria. All patients had low urinary citrate levels. Two had defects of the renal concentrating mechanism, one of whom had potassium depletion. In one patient classic renal tubular acidosis subsequently developed. The ability to lower urine pH was tested by acute and chronic ammonium chloride loading and by sodium sulfate infusion. In two patients minimum urine pH after sodium sulfate infusion was approximately 1 pH unit lower than after ammonium chloride loading. In one patient sodium restriction prior to acute ammonium chloride loading interfered with the patient's ability to lower urine pH. A possible mechanism for the defect in ability to generate a steep blood-to-urine hydrogen ion gradient in patients with renal tubular acidosis is suggested. © 1968.