Studies in Urolithiasis: II. Relationships Between Pathogenesis, Structure and Composition of Calculp

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Abstract
A crystallographic study of the various phenomena and mechanisms of calculogenesis was made from the standpoint of crystallography because the process is one of crystallization. A table of crystalline substances found in 1000 urinary calculi is presented. Crystallographic study of the structure and composition of the nuclei of calculi is done by dissection with a needle under binocular stereoscopic vision, the crystalline material being identified by the use of optical polarization techniques. The nuclei of Ca oxalate monohydrate calculi are composed of that substance or of apatite. Some of the calculi have a concavity on one surface with a structure which may be a pedicle in the bottom suggesting origin from a surface such as the renal papilla. It is believed that some calculi originate from an attachment to the renal papilla, as described by Randall. Papillary encrustations were produced experimentally in rats. It is not believed that all Ca oxalate monohydrate calculi originate in this manner; those with a central nucleus and symmetrical concentric layers are believed to originate by crystallization from supersaturated urine. No evidence has been found to support the theory that foreign bodies, such as desquamated epithelium, act as the nucleus for renal calculi. Ca oxalate dihydrate calcui do not appear to have a nucleus. Study of the nucleus of calculi composed of apatite and magnesium ammonium phosphate hexahydrate is less satisfactory because of irregularity of the calculi. All phosphatic calculi are not associated with urinary infection, particularly in the early stages. The metal cation rather than the acid radical is most important in a consideration of calculi from the standpoint of pathogenesis. Apatite calculi should not be grouped with other phosphatic calculi because they commonly occur in an acid urine. By optical crystallographic study it is possible to correlate pathogenesis with composition and structure of various types of calculi. It is often possible to reconstruct the clinical history by an optical study of the calculus obtained from the patient.