Value of Bone Mineral Analysis in Patients with Urolithiasis by Single Photon Absorptiometry, Dual Photon Absorptiometry, and Dual Energy X-Ray Absorptiometry — Comparison of Primary Hyperparathyroidism and Idiopathic Urolithiasis, and on the Possibility of Differentiating Idiopathic Hypercalciuria

In the investigation of urolithiasis, it is very important to examine bone which contains most of the calcium (Ca) in the body. Bone mineral density (BMD) has hitherto been measured with a microdensitometry (MD) technique1 or a single photon absorptiometry (SPA) technique in patients with primary hyperparathyroidism (PHP)2-4 and idiopathic urolithiasis5-7. These reports show that 2 types of idiopathic hypercalciuria (IC) — renal hypercalciuria (RH) and absorptive hypercalciuria (AH) — can be differentiated with the MD or SPA technique. The differential diagnosis of IC, which is a very important cause of urolithiasis, is now performed by the Ca restriction and load test (so-called Pak test)8, but the test is time-consuming and demanding. So, assessment of BMD as a substitute for the Pak test might be preferable. However, bone fractures first occur in vertebral bones, and later in peripheral bones in metabolic bone disease, including primary hyperparathyroidism,9, 10. Because the dual photon absorptiometry (DPA) technique,which uses 2 different energy types of γ-ray, and dual energy X-ray absorptiometry (DEXA), which uses two types of X-ray but does not use radioisotope, can examine the BMD of deep bone11, these are more useful to examine BMD in IU patients than SPA and MD. In this report, BMD of patients with PHP and IU were assessed by SPA, DPA, and DEXA techniques simultaneously and the data obtained with the 3 techniques compared.