In vitro calcium oxalate crystallisation methods.

In vitro calcium oxalate crystallisation has been, and will continue to be, of fundamental importance to urolithiasis research. Many different methods have been employed which differ qualitatively and quantitatively in the extent that they reproduce aspects of the renal system or in their ability to distinguish different aspects of crystallisation activity. Whatever system is used there are three key aspects that are worth bearing in mind. Firstly, a major controlling factor will be the prevailing supersaturation and other physicochemical considerations, secondly, during the course of the reaction different processes may come into play and thirdly, the processes we are trying to model take place in a dynamic biological environment. Different approaches to the study of crystallisation can be classified in many ways, such as the process or analytical technique but at a more fundamental level it is helpful to focus on the changes in supersaturation during the course of the reaction. A steady state supersaturation is more likely to be representative of the intra-renal situation than a system which decays to the equilibrium position. The constant composition method and the mixed suspension mixed product removal method both achieve a steady supersaturation.