Determination of urinary calcium oxalate crystallization mechanisms and kinetics using flow cytometry

This paper describes the application of flow cytometry to the determination of calcium oxalate crystallization kinetics and mechanisms in real urine. The technique has the unique advantage of simultaneously providing quantitative particle number-size distributions and qualitative data concerning particle structure and morphology. Twenty-four-hour urines from 10 healthy male subjects were treated with sodium oxalate and the ensuing crystallization of calcium oxalate was monitored by flow cytometry. In 7 specimens crystallization was accompanied by increasing size and by a fundamental change in particle morphology. This suggests that nucleation and aggregation occurred in these specimens. In the remaining 3 samples, increasing particle numbers occurred without any changes in size or morphology, indicating that nucleation was the sole mechanism in these specimens. These results demonstrate that flow cytometry is able to differentiate between nucleation, growth and aggregation mechanisms thereby making it an extremely useful analytical tool for stone researchers.