Determination of urinary calculi by binocular stereoscopic microscopy.

Because of the inadequacies of chemical methods for identifying urinary calculi, mineralogical methods have been developed, but these methods are sometimes time consuming and expensive. The aim of the study was to evaluate urinary calculi with binocular stereoscopic microscopy (BSM), X-ray diffraction (XRD), scanning electron microscopy (SEM), and biochemical methods and to determine the specificity of BSM. A total of 30 pediatric patients with urinary calculi (17 girls and 13 boys), from 6 months to 19 years of age, were included in the study. The calculi obtained were evaluated with a Novex-AP 8 BSM, a Shimadzu 6000 XRD device, a Jeol JXA 733 SEM, and a biochemical kit from Merck. In 2 cases BSM rapidly determined that the material was not from the urinary system. Except for 2 cases, BSM results were identical to the results obtained by XRD. In 2 non-identifiable cases, the samples were struvite with an amorphous structure. The sensitivity of BSM was 93%. The small size of calculi did not permit biochemical analysis in 4 cases. In another group of 4 cases, the results of biochemical analysis did not agree with the XRD. In 7 cases, calcium phosphate was found by biochemical assay, although it was not confirmed by XRD. The sensitivity of biochemical analysis was 58%. BSM is more reliable than biochemical methods. BSM can be used for a rapid, reliable evaluation of the urinary calculi. It gives additional information about the nidus, the crystalline structure, and the order of deposition of components. The clinician can perform this investigation himself, obtaining very useful information about stone formation that allows an immediate start of medical treatment, decreasing recurrences.