Solubility, inhibited growth and dissolution kinetics of calcium oxalate crystals in solutions, containing hippuric acid.

An analysis of crystal growth and dissolution of slightly soluble salts in physiological solutions in the presence of complexing ions was carried out, simulating conditions typical in human urine. It was found that hippuric acid, a normal physiological constituent of urine, acts at increased concentrations as a dissolving agent with respect to calcium oxalate (CaOx) and CaOx calculi. The kinetics of dissolution of crystalline CaOx calculi in physiological solutions containing hippuric acid at different concentrations were studied, using the change in the Archimedean weight of samples immersed in the solution. Analysis of the experimental results enabled the determination of the increased solubility of CaOx in the presence of hippuric acid and the quantitative characterization of this substance as a new and promising agent for dissolving CaOx calculi in human urine. The possible effect of hippuric acid as a natural regulator of CaOx supersaturation and crystallization in human and mammalian urine is also discussed.