In vitro crystallisation systems for the study of urinary stone formation.

Various methods and techniques are aimed at modelling crystallisation processes of urinary stone formation in vitro. There are considerable differences between them in technical and physico-chemical principles, quantification of crystal nucleation, growth and agglomeration and the parameters measured. In this paper, some important in vitro systems are described as examples. They are compared with regard to some of their features and capabilities. Emphasis has been placed on evaluation of the physiological relevance of the methods. For that reason, the different in vitro models have been related to current views on intrarenal in vivo, mechanisms underlying stone formation and other independent experimental results. Crystallisation procedures carried out in aqueous solutions are likely to mimic crystalluria, corresponding to a free-particle mechanism. However, a specifically tailored flow technique of crystallisation in gels seems to be a reasonable model of stone formation, in accordance with the generally accepted fixed-particle theory.