Comparison of Growth Kinetic of Urinary Crystallites from Patients with Calcium Oxalate Stones with that from Healthy Subjects

The differences of growth kinetic of urinary crystallites from patients with CaOxa stones and healthy subjects were compared. With the increase of crystal growth time (t), the size of urinary crystallites from patients increased constantly from 10±9 μm att=1 h to 50±45 μm att=72 h, but the number of urinary crystallites decreased gradually from 1820±610 ind./mm2att=1 h to 220±98 ind./mm2att=72 h, indicating that the formation process of crystallites in lithogenic urine was ascribed to growth control. In contrast, for healthy subjects, the number of crystallites increased from 1650±850 ind./mm2att=1 h to 1800±830 ind./mm2att=72 h. However, the particle size was slowly increased from 7±5 μm att=1 h to 14±13 μm att=72 h, while the sizes of most urinary crystallites were still less than 20 μm, indicating that the growth process of crystallites in healthy urine was dominated by nucleation control. The differences mentioned above are mainly attributed to that both the concentration and the activity of the inhibitors in healthy urine were higher than those in lithogenic urine, and the inhibitors in healthy urine can inhibit the growth and aggregation of urinary crystallites more effectively. This result can help to elucidate the renal-calculi formation mechanism.

Composition and Morphology of Nanocrystals in Urines of Lithogenic Patients and Healthy Persons

The composition and morphology of nanocrystals in urines of healthy persons and lithogenic patients were comparatively investigated by means of X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was shown that the main composition of urinary nanocrystals in healthy persons were calcium oxalate dihydrate (COD), uric acid, and ammonium magnesium phosphate (struvite). However, the main compositions of urinary nanocrystals in lithogenic patients were struvite,β-tricalcium phosphate, uric acid, COD, and calcium oxalate monohydrate (COM). According to the XRD data, the size of nanocrystals was calculated to be23∼72 nm in healthy urine and12∼118 nm in lithogenic urine by Scherer formula. TEM results showed that the nanocrystals in healthy urine were dispersive and uniform with a mean size of about 38 nm. In contrast, the nanocrystals in lithogenic urine were much aggregated with a mean size of about 55 nm. The results in this work indicated that the urinary stone formation may be prevented by diminishing the aggregation and the size differentiation of urinary nanocrystals by physical or chemical methods.