[Component analysis of urinary calculi in the etiologic diagnosis of urolithiasis in the child].

The potential risk of recurrence and degradation of renal function justifies the etiological investigation of all lithiasis-associated pathologies. Therefore calculus analysis of the crystalline phases and morphological characteristics is an important factor in the etiological diagnosis of the disease. Microscopic examination and infrared spectroscopy of calculi from 727 children showed that calcium oxalate was the main component in 36.7% of cases, followed by calcium phosphate (31%), struvite (9.9%) and purine groups (7.7%). The most frequently observed crystalline from was carbapatite (26%), then whewellite (21%) and weddellite (15.7%). As regards the etiopathogenic aspect in adults, the relations between hypercalciuria and weddellite, and between hyperoxaluria and whewellite are also found in the child: in subjects with hypercalciuria, 82% of the calculi contained over 20% weddellite; and in subjects with hyperoxaluria, whewellite was the major constituent in 79% of cases (or 95% in the absence of associated hypercalciuria). In 27 calculi mainly composed of whewellite, the morphological analysis indicated primary hyperoxaluria; this diagnosis was confirmed in 25 cases by specific biological investigation. Urinary tract infection is frequently associated with lithiasis, but its lithogenic role cannot be confirmed without calculus analysis. Several criteria can be used as markers to determine the lithogenic etiology of the infection, i.e., the presence of struvite, the carbonate rate of carbapatite, and the whitlockite and/or protein content of the calculus.