[Nomograms for calculating the degree of urine saturation with lithogenic compounds]

Studies with computed calculation of an equilibrium chemical composition (57 particles) and saturation of urine according to 12 compounds which are components of uroliths, showed that to appraise the risk of lithogenesis, orientation on the saturation of uric acid with calcium oxalate and hydroxyapatite is sufficient in most cases. An index of the degree of urine saturation is suggested, its physical meaning corresponds to the ratio of the amount of the dissolved lithogenic compound to its threshold solubility at the given temperature, which makes it possible to compare the saturation with compounds differing in the stoichiometric coefficient. Nomograms have been elaborated to reduce the volume of analytic studies and simplify the calculations. They take into account the revealed relation between the degree of saturation for each compound and 3-4 principal physicochemical urine parameters. The supersaturation thresholds are determined, when these are exceeded, the risk of lithogenesis can be predicted with a probability of no less than 0.8.