Clinical implications of physicochemistry of stone formation

Urinary stones are composed of crystalline material usually associated with a matrix of organic material. Irrespective of the type of stone, such as calcium-salts, struvite, uric acid, or cystine, crystallization is a first step in their formation. The kidney contains several mechanisms by which it can steer the outcome of the crystallization process into a direction that is harmless. To appreciate how these mechanisms work, how they can be disturbed and how we might effect them, we need to understand the basic principles of crystallization and translate these to the conditions existing in the urinary tract. This review will deal step by step with the crystallization process, from supersaturation to nucleation, crystal growth, crystal agglomeration and stone growth and for each step describe how it can proceed in the urine, how it may contribute to stone formation and which laboratory techniques are available for investigating them. In so doing, it is important to realize that the different steps we recognize in the overall crystallization process occur simultaneously and can all affect each other. This makes interpreting the outcome of a crystallization process a complex task [1].