A study of calcium oxalate crystallization in kidney stone formation

This work was undertaken to gain a fundamental understanding of the physical and chemical mechanisms involved in the formation of kidney stones. Calcium oxalate is the major component of kidney stones and was chosen as the representative of stone minerals. Experiments were performed in a mixed-suspension, mixed-product-removal (MSMPR) crystallizer and in a flow chamber crystallizer.; Previous work has shown the significant influence of urinary macromolecules on calcium oxalate crystallization. Both inhibition and promotion of crystal growth and crystal aggregation by these biopolymers has been reported; however, crystal growth and crystal aggregation mechanisms were not isolated in these studies. In work conducted with the MSMPR crystallizer, the linear population density model has been used to describe nonlinear data; crystal growth rates were obtained but crystal aggregation was neglected. Crystal aggregation has been suspected as being important in stone formation.; In this work, experiments with the MSMPR crystallizer were conducted to characterize calcium oxalate crystallization. The entire MSMPR crystallization process was characterized by unsteady state, quasi-steady state, and steady state periods. At unsteady state, nucleation, crystal growth, and crystal aggregation all occurred in the system. In passing from the unsteady to the steady state, the crystallization process progressed with reduced nucleation and crystal aggregation. At steady state, only crystal growth was important. The unsteady state operation of the MSMPR crystallizer was of interest due to the presence of crystal aggregation; however, a clear understanding of the crystal aggregation mechanism depends upon knowing crystal growth kinetics.; An approach was developed to obtain crystal growth rate for the entire process, including unsteady and steady states, by identifying the shifts of particle size distributions along the x-axis with time. The growth rates obtained from this method correlated well with the results of the linear population density model and the experiments with a flow chamber crystallizer. With this method, a model urinary biopolymer, poly-L-glutamate (PGA), was identified as a growth rate inhibitor.; The flow chamber crystallizer experiments were conducted to investigate the effects of healthy and injured cultured epithelium (Maden Darby Canine Kidney (MDCK) cells) on the growth of single calcium oxalate crystals in the prescence of flow shear. Healthy MDCK cells were found to inhibit crystal nucleation. The crystal growth rate of calcium oxalate monohydrate (COM) decreased in the order of crystal growth on glass {dollar}>{dollar} MDCK cells treated with HCl {dollar}>{dollar} MDCK cells treated with papain {dollar}>{dollar} healthy MDCK cells. The biopolymer additive, heparin, inhibited COM crystal growth on healthy MDCK cells.