Renal calculi associated with incomplete distal renal tubular acidosis

We report 5 cases of renal calculi associated with incomplete type I renal tubular acidosis. The patients presented with a history of recurrent calculi and demonstrated bilateral calculi with corticomedullary junction calcification on x-ray. Stone analysis revealed primarily calcium phosphate stones and metabolic studies demonstrated hypercalciuria, mild depression of serum bicarbonate and inability to lower the pH of a fasting morning urine to less than 5.8. The 24-hour urinary citrate excretion was depressed markedly. The diagnosis was confirmed by an ammonium chloride loading test. Treatment consisted of alkalization of the patients, which corrects the hypercalciuria and increases the urinary citrate level and should decrease the tendency to form stones. The diagnosis of incomplete type I renal tubular acidosis should be considered in patients with recurrent renal calculi.