Long-term allopurinol treatment of recurrent renal stones associated with idiopathic renal hypouricemia

Abstract

A 42 year-old man who had had recurrent renal colic episodes since he was 25 year-old was found to have hypouricemia at the age of 37. Several times he passed tiny stones composed mainly of calcium oxalate. X-rays showed staghorn stones in both kidneys. Physical examination disclosed no abnormality. Routine hematological and blood chemistry values were all within the normal range, except for a low uric acid level (1.9 mg/dl). The creatinine clearance was 88.4 ml/min and uric acid clearance ranged from 50.7 to 53.3ml/min. The average urinary uric acid excretion was 482.5 mg/24hr on a low purine diet. There was neither glycosuria nor abnormal amino acid pattern in urine. The urinary calcium excretion ranged from 158.4 to 306.0 mg/24hr under a regular hospital diet. Administration of pyrazinamide almost completely suppressed uric acid excretion, while that of benzbromarone did not cause a significant change in uric acid excretion. These suggested that the hypouricemia in this patient was caused by the defect in tubular reabsorption of uric acid at the postsecretory site.
Since hyperuricosuria was suspected to be one of the causes contributory to the formation of calcium oxalate stone, this patient was given allopurinol therapy. Although 8years administration of allopurinol (200mg/day ) did not reduce the renal calculi on X ray film, it relieved him of stone discharge with colic. Therefore, we conclude that allopurinol may be beneficial in the present case and it may be applicable to some patients who suffer from recurrent colic of renal calcium oxalate calculi associated with idiopathic renal hypouricemia.