Simple test to evaluate the risk of urinary calcium stone formation

A simple test to evaluate the capacity of a urine to crystallize calcium salts is presented. The test is based on the fact that if a non-protected non-renewed surface remains in contact with a urine, sooner or later the contained supersaturated substances crystallize on it. Thus, by using an adequate surface, it is possible to derive a period within which a normal urine does not crystallize whereas a lithogenic urine induces the growth of calcium salts. The test was applied to urines of oxalocalcic stone-formers and healthy people and showed an excellent discrimination between clearly abnormal and healthy urines. Semiologic analysis of the data is also included.