X-ray diffractometric analysis of L-cystine stones in 12 patients.

: In 12 of 21 cystinuric patients, the components of cystine stones, either previously passed or removed at surgery, were studied by X-ray diffractometry and chemical analysis. The results of diffractometry suggested that, in addition to cystine, the stones contained sodium urate and ammonium magnesium orthophosphate hydrate, although chemical analysis was negative for these components. The role of uric acid in cystinuria is discussed.