An Oral Calcium Tolerance Test for the Diagnosis of Hypercalciuria in Patients with Calcium Nephrolithiasis

Kang, Jeng Gi; Yoon, Jong Byung

Abstract

Hypercalciuria is the most common metabolic abnormality in patients with calcium nephrolithiasis and oral calcium tolerance test (OCTT) has been developed to diagnose various forms of hypercalciuria. 71 patients with calcium nephrolithiasis who had been admitted to the Dept. of Urology, Pusan National University Hospital during the period of 11/2years from Jan. 1984 to Jun. 1985, were studied for urinary calcium excretion by OCTT constituted of rigorous calcium restriction for 3 days, fasting and calcium loading. The following results were obtained. 1. Of the 71 patients, hypercalciuria was found in 43 cases (61%) and hyperuricosuria in 24 cases (33.8%). Hyperuricosuria was found more frequently in patients with hypercalciuria than patients with normocalciuria. 2. Of 43 cases with hypercalciuria, 11 cases (15%) were classified as absorptive type I, 14 cases (2O %) as absorptive type II 9 cases (13%) as renal hypercalciuria, and 3 cases (4%) as primary hyperparathyroidism. In the other 6 cases, the etiology of the hypercalciuria could not be defined by our simple OCTT. 3. In fasting, urinary Ca/Cr ratio was 0.052+/-0.025 in normocalciuria group, 0.068+/-0.018 in absorptive type I, 0.068+/-0.025 in absorptive type II group, and all these values were in normal limit. In renal hypercalciuria and primary hyperparathyroidism group, the ratios were 0.167+/-0.033 and 0.149+/-0.029, and these values were significantly higher than normal range. 4. After calcium loading, urinary Ca/Cr ratio was 0.105+/-0.041 in normocalciuria group, but in hypercalciuria groups, the ratios were markedly increased to 0.244+/-0.035 in absorptive type I, 0.288+/-0.042 in absorptive type II, 0.263+/-0.068 in renal hypercalciuria, 0.290+/-0.041 in primary hyperparathyroidism group. 5. In renal hypercalciuria, the ratio of renal calcium reabsorption was 97.8+/-O.9%, and tend to be lower than other subgroups of hypercalciuria and normocalciuria group. The ratio of renal phosphorus reabsorption did not show the difference of the values among the subgroups of hypercalciuria and normocalciuria group. OCTT using rigorous calcium restriction for 3 days is recommended as a relatively simple and reliable method of defining the etiology of hypercalciuria.