Studies in Urolithiasis: I. The Composition of Urinary Calculi

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Abstract
Because the chemical analysis of urinary calculi is unsatisfactory, a study was undertaken by means of polarized light and x-ray diffraction photography. The crystalline components of urinary calculi (as found in this study) are: Ca oxalate monohydrate (whewellite), Ca oxalate dihydrate (weddelite), Mg ammonium phosphate hexahydrate (stru-vite), carbonate-apatite and hydroxyl-apatite (collectively called apatite), Ca hydrogen phosphate dihydrate (brushite), uric acid, cystine and Na acid urate. The appearance, associations and optical constants of these substances are given. A determinative table, photographs, x-ray diffraction photographs and x-ray spacing data are presented. Ca carbonate, cholesterol, xanthine and indigo were not found in a series of approx. 700 calculi. Pure Ca oxalate calculi constituted 36.1% of the total; mixed Ca oxalate-apatite calculi comprised 31.0%; together they composed 67.1% of the total. These calculi usually (but not always) occur in acid sterile urine. Pure magnesium ammonium phosphate hexahydrate, pure apatite and mixed magnesium ammonium phosphate hexahydrate-apatite calculi comprised 19.5% of the total. These calculi usually (but not always) occur in alkaline infected urine. Ca hydrogen phosphate dihydrate occurred in 1.6% of the calculi. Uric acid and cystine exist more frequently in pure than mixed form and occurred in 6.1% and 3.8%, respectively, of the series. Na acid urate occurred but once in the series and in microscopic amount. It was the only urate found. The methods of optical and x-ray crystallography provide powerful tools for study of various aspects of calculous disease.