Monitoring methods has been proposed for calcium oxalate crystal formation in model systems containing urine of patients with oxalate urolithiasis, which allow to evaluate main phases of crystal formation.

Crystal formation activity of urine was evaluated in 112 patients with oxalate urolithiasis, which was nonrelapsing in 69 persons (40 male and 29 female). In 43 patients (27 male and 16 female) relapsing form of oxalate urolithiasis was detected. As a control biochemical measurements from 135 apparently healthy individuals (61 male and 74 female) at the age of 21-62 without any urological disease were analysed. Crystal formation dynamics in patients with oxalate urolithiasis demonstrated lower initial nucleation rate in comparison with healthy individuals. At the same time aggregation phase was more evident in these patients when compared with healthy individuals. Initial crystal formation delay in diseased subjects unlike healthy depends on initially high concentration of total calcium and particularly ionized calcium and uric acid in urine.

The patients had higher concentrations of total calcium, ionized calcium, uric acid, oxalates and lower level of citrates in urine when compared to healthy individuals. Initial crystal formation delay in patients with oxalate urolithiasis may be considered as a result of injury of compensatory mechanisms which prevent urine oversaturation by lithogenous substances. In healthy individuals these mechanisms provide fast “discarding” of lithogenous ions (calcium and oxalate) excess to microcrystals which have no liability to further growth and aggregation.