Crystalluria and its possible significance. A patient-control study.

The significance of crystalluria in the diagnosis and prognosis of urolithiasis remains a controversial subject in the current urological literature. In this study, in addition to the standard urolithiasis clinical and biochemical work-up, routine urine microscopy was performed to study crystals in 1 fresh and 2 stored morning urine samples from 140 urinary stone patients and 42 controls. Crystalluria was more frequently detected in patients (9.3% of the fresh samples) than in controls (2%). Storing the samples for 6 hours did not increase the frequency percent of detected crystalluria either in patients or controls. However, in the samples stored for 24 hours, the frequency of crystalluria increased to 27.1% in patients and only to 12% in controls, though the pH did not change from that of the fresh sample. In addition, while calcium oxalate crystals in patients formed aggregates whether in fresh or 24 hour samples, those of controls did not. This denotes a characteristic change in the physico-chemical properties of the urine of stone formers from that of controls. Accordingly, the study of crystalluria in patients with urolithiasis seems to help in the proper evaluation and, maybe, treatment of the disease.