Simple classification of renal calculi closely related to their micromorphology and etiology

BACKGROUND: Classification of renal calculi with clear correlation with the main urinary etiological conditions has been previously established. However, such information is complex and difficult to adapt to clinical routine practice. METHODS: A simple classification of renal calculi based on their structure and composition is proposed and applied to 2500 renal calculi to achieve the percentage of each category. The urines of 700 individuals chosen randomly have been analyzed and the results compared with those obtained with 51 healthy subjects. RESULTS: 12.9% calculi corresponded to calcium oxalate monohydrate papillary calculi, 16.4% to calcium oxalate monohydrate unattached calculi, 33.8% to calcium oxalate dihydrate calculi, 11.2% calcium oxalate dihydrate/hydroxyapatite mixed calculi, 7.1% hydroxyapatite calculi, 4.1% struvite calculi, 0.6% brushite calculi, 8.2% uric acid calculi, 2.6% calcium oxalate/uric acid mixed calculi, 1.1% cystine calculi and 1.9% various infrequent calculi. Based on the corresponding urinary analytical studies, each kind of calculus is related with the more frequently associated urinary alterations. CONCLUSIONS: An important aspect of this classification is the possibility to establish, by means of the correct study of the calculus, some of the main possible etiologic factors closely related to its formation.