Aim.In clinical practice urolithiasisis usually confirmed byX-ray techniques or by an indication ofstone discharge. However, this approach does not allow to detect the stages preceding concrement formation. In order to evaluate the morbidity risk and the effectiveness of treatment, it is necessary to estimate the activity ofstone formation. A large number of diagnostic tests and coefficientsfor calculating urinary ion activity index (UIAI)were proposed, which comprise the relationship between promotors and inhibitors ofstone formation. The АP[CaOx] index proposed by H.G. Tiselius was approved in 2010, which is based on a relationship between lithogenic and anti-lithogenic properties of urine. Other well-known methods of UIAI calculation, which are possible to employ with the EQULL and JESS soware, are based on models of thermodynamic equilibrium and operate up to 23 variables. Due to the high number of variables and the need for computing equipment, these techniques were not brought into common use. e attempts to simplify the technique have led to the development of other methods of calculation: the Bonn risk index (BRI), urinary relative supersaturation (URS), initial speed of crystal formation (ISCF) and the simplified Tiselius index.

Materials and methods. For UIAI calculation, as proposed by H.G.Tiselius (an approved method for evaluating the risk ofstone formation),we used Mathcad V.15 software, which is aimed at preparation of interactive documentsfollowed by mathematical analysis and visual graphic representation, which can be transformed into a normogram.

Results. We have calculated the matrices of UIAI variables using the mathematical software Mathcad V.15.Agraphical presentation of a simple normogram reflecting a risk of urolithiasis was also created.

Authors declare lack of the possible conflicts of interests.