Kinetics of Dissolution of Calcium Oxalate Calculi in Physiological Solutions Containing Hippuric Acid

Abstract

An analysis of the thermodynamics and kinetics of crystal growth and dissolution of slightly soluble salts in physiological solutions in the presence of complexing ions is made, accounting for conditions typical in human urine. It is found that hippuric acid, a normal physiological constituent of urine, acts at increased concentrations as a dissolving agent with respect to calcium oxalate and calcium oxalate calculi. The kinetics of dissolution of crystalline calcium oxalate calculi (CaOx) in physiological solutions containing hippuric acid in different concentrations is studied, using the change in the Archimedean weight of samples, immersed in the solution. The analysis of the experimental results enables the determination of the increased solubility of CaOx in the presence of hippuric acid and to characterize quantitatively this substance as a new and very prospective dissolving agent of CaOx calculi in human urine. A discussion is also given on the possible effect of hippuric acid as a neutral regulator of CaOx-supersaturation and crystallization in human and mammal urine.