Observations Upon Calcium Oxalate Crystallization Kinetics in Simulated Urine

Abstract

Two major etiologic theories of urinary stones [in humans] are excessive saturation of urine with crystallizable substances or defects in inhibitors that allow relative supersaturation to occur. To date, it has been difficult to confirm the supersaturation theory in experiments using diffusion-limited crystallization systems because direct measurements of the nucleation process of crystallization could not be performed. Well developed, continuous crystallizer techniques were used and adapted from industrial use to the study of stone disease. Data derived from the experiments allowed the absolute measurement of crystal growth rate and determination of nucleation rate. These methods were applied to study the calcium oxalate dihydrate (weddellite) system in artificial urine that lacked only proteinaceous components. It was not possible to grow crystals large enough within 5-20 min to obstruct the collecting ducts of the kidney. Other processes, such as aggregation or stasis within tissues, may be related to initiation of stone disease. Nucleation rate exceeded growth rate. Multiple small particles were created at the expense of allowing larger particles to grow. Inhibitors can be tested rapidly in this system by adding them in concentrations compatible with those found in urine.