Physicochemical background for ambiguity of clinical recommendations in treating phosphate nephrolithiasis.

Efficiency of clinical recommendations for curing and prevention of phosphate nephrolithiasis founded on physicochemical investigations is unexpectedly low and apparently did not exceed 50%. We tried to consider possible physicochemical causes of this fact. For this purpose the influence of changes of urine pH and of calcium, phosphate and complexon concentrations on the probability of different precipitation phases of solid calcium phosphate has been reviewed. The importance of tendencies of changing the urine dynamic physicochemical parameters such as the precipitation induction period and the amplitude of urine pH variations in time has been shown. It was established that the probability of the existence of Ca3(PO4)2, Ca8H2(PO4)6.5H2O, CaHPO4.2 H2O and MgNH4PO4.6 H2O in urine depends on the time of its transition from the supersoluble state and is determined in the final analysis by the relationship of formation rates and solid phase dissolution rates. This was verified by experiments and by data obtained in the clinical laboratory.

Urine pH variation dynamics in healthy individuals and stone formers.

Urine pH density distribution curves have been obtained in groups of patients with concrements of various chemical compositions. Quantitative regularities for mixing chemical compounds in the concrements established by the infrared spectroscopic method have been shown to agree with urine pH distribution density (in time). Potential physicochemical mechanisms for the revealed generality are considered. In particular, it is indicated that urine pH variations display in the first approximation buffer effect of the concrement components. A Fourier analysis of pH variations in the homogeneous urine of healthy individuals and in the systems of urine versus concrement as a time function has been made. Urine pH variations observed have been shown to be approximated by the superposition of harmonic vibrations with a range of frequencies multiple of the diurnal one. It has been found that a distinctly pronounced and complicated gamut of pH fluctuations over the entire physiological range of values (i.e. 4.5-8.5) is typical of healthy individuals in contrast to the stone formers.