The Saturation of Urine in Recurrent, Idiopathic Calcium Stone-Formers

Abstract

It has been shown recently that sodium urate, and to a lesser extent uric acid, are nucleators of calcium oxalate crystallisation in vitro, and it has been suggested that this may account for the initiation of calcium oxalate stones in a considerable proportion of idiopathic stone-formers (1, 2). For these salts to act as heterogeneous nucleators, urine must be sufficiently supersaturated to permit spontaneous precipitation of one or other of them. Furthermore, urine must also be adequately supersaturated with calcium oxalate to allow nucleation and growth of calcium oxalate on the urate nuclei. This study was carried out to measure the saturation of urine of calcium stone-formers with calcium salts and with the various urates in order to determine which salts, if any, are likely to precipitate spontaneously from urine, and whether it is feasible, or even necessary, to invoke urates in the nucleation of calcium salts.