The Structure and Formation of Urinary Calculi: I. Oriented Crystal Growth

SUMMARY Compounds present in urinary stones have a wide range of textures and each substance does not necessarily have the same texture even in the same stone. In calculi, oriented crystal growth has been found for most of the constituents including uric acid, uric acid dihydrate, whewellite, weddellite, xanthine, cystine, ammonium acid urate, struvite and brushite. In many stones which contain areas of these pure substances, crystal growth is such that a prominent crystallographic axis is perpendicular to the preceding band of material. The crystals though are randomly oriented about this axis. In stones consisting of layers of different composition, the oriented growth of one layer on another has also been observed. Oriented crystal growth could, therefore, be an important factor in the formation of urinary calculi.