Observations on in vitro and in vivo calcium oxalate crystalluria in primary calcium stone formers and normal subjects.

Fresh urine samples from stone formers (SF) and normal subjects (N) were rapidly evaporated at 37 degrees C to 1200 mosmol/kgH2O and the particle size distribution of the formed particles studied by Coulter Counter and chemical methods. No significant difference was found between the two groups in their relative supersaturation of calcium oxalate at the point of spontaneous precipitation. SF and N urines seem to have an equal driving force for particle precipitation. The major difference between them was in the volume of particles with diameters greater than 11.4 microns. SF urines showed an approximately 5-fold increase in total particle volume (after evaporation) and N urines had about a 2-fold increase over the volume in the freshly voided urine samples. The total volume of large particles (greater than 11.4 micron) increased more than 7-fold in SF urine while only a 2-fold increase was detected in the normal urines after evaporation.