[The usefulness of computerized axial tomography (CT) in establishing the composition of calculi].

Determining stone composition before extracorporeal lithotripsy can be potentially useful. A total of 90 calculi of 6 different chemical composition (calcium oxalate monohydrate, calcium oxalate dihydrate, magnesium ammonium phosphate, phosphate carbonate, uric acid and phosphate oxalate) were analyzed in vitro using computed tomography (CT). The mean, central, peripheral, maximum, minimum stone density and stone morphology were determined. At least in vitro, the serial analyses of the mean, minimum, central stone density and stone morphology permitted distinguishing these 6 types of calculi, although 53% of the calcium oxalate dihydrate calculi could not be distinguished from the phosphate oxalate stones.