[Studies on an oral calcium loading test in upper urinary tract stone formers]

An oral calcium loading test was performed on 55 patients with upper urinary tract stones to find absorptive or renal hypercalciuria. The mean urinary calcium excretion level of this patient group was significantly greater than that of a control group of 10 patients without abnormal upper urinary tract. Idiopathic hypercalciuria defined as more than 250 mg per day in males and more than 200 mg per day in females was observed in 13 patients; 4 patients with absorptive hypercalciuria, 6 patients with renal hypercalciuria and 3 patients of origin-unknown hypercalciuria. Five of the 6 patients with renal hypercalciuria had recurrent and/or multiple urolithiasis. From these results, this test was considered to be useful in the discrimination between absorptive and renal hypercalciuria.