Abstract: Objective In order to seek the methods in the prevention and cure of urinary negative stones, the compositions of stones and the zeta potential of their urinary crystallites were analyzed. Methods Twenty-five negative stone samples were investigated by XRD and FT-IR. The zeta potential of urinary crystallites in lithogenic urines were investigated by nanoparticle size analyzer and were compared with 30 samples of healthy subjects. Results 24 cases of the negative stones mainly consisted of uric acid in which 6 cases containing a small quantity of calcium oxalate. Only one sample was ammonium urate. The urine pH of the negative stone formers, with an average of 5.25±0.26, was lower than that of the healthy subjects with an average of 6.06±0.41. The Zeta potential of urinary crystallites in 25 lithogenic patients was -5.04±3.48 mV, which being higher than that in normal subjects (-10.27±1.35 mV). Conclusions The urine pH of urinary negative stone formers was lower than that of the healthy subjects, but there is on difference between them (P>0.05). The Zeta potential of urinary crystallites in negative stone formers (with an average of -5.04±3.48 mV) was higher than that in healthy subjects (with an average of -10.27±1.35 mV), there is difference between them (P<0.05).

Key words: Urinary negative stone, urinary crystallites, pH, Zeta potential