Influence of urine pH on stone formation processes in urolithiasis

Introduction. Urine pH is one of the key indicators to assess the activity of lithogenesis processes in urolithiasis patients. Urine pH is one of the significant markers signaling the presence of pathological changes both in the body as a whole and in the urinary system in particular. On the other hand, urine pH remains one of the key parameters that regulate the state of the urinary system and determine the type of metabolic lithogenic disorders. The aim of the study was to assess the effect of urine pH on the formation of stones of various chemical composition and on the level of urinary excretion of the main stone-forming substances. Materials and methods. The study examined data from 708 urolithiasis patients (303 men and 405 women). All patients underwent biochemical analysis of blood, biochemical analysis of daily urine, determination of the chemical composition of urinary stones. Results. The incidence of uric acid urinary stones decreases as urine pH rises from 42.3% (pH1) to 2.6% (pH8) (p = 0.0000004). The maximum level of excretion of uric acid with urine was recorded in the urine pH range of 5.6-5.9 (pH4) and amounted to 3.814 mmol/day. The frequency of calcium oxalate stones occurrence increased in the ranges of pH 5.1-5.9 and 6.1-6.5. In the pH range 5.6 - 6.1 and 6.5 - 9.0, a sharp decrease in the incidence of calcium oxalate urinary stones was recorded. The maximum level of urinary calcium excretion was recorded at urine pH 5.6-5.9. The prevalence of carbonate aptite urinary stones increases with increasing urine pH. This tendency can be traced especially clearly in the urine pH ranges of 5.6 - 6.5 (from 23.0% to 50.8%, respectively). The highest level of phosphaturia (29.149 mmol / day) was observed at urine pH 5.6-5.9. In the intervals of urine pH 6.6-9.0, there was a sharp increase in the incidence of struvite calculi (19.3-36.8%, respectively) (p = 0.00004). Conclusion. The urine pH is one of the main factors affecting lithogenesis. It is important to monitor the urine pH figures and, if necessary, to correct these parameters conducting urolithiasis metaphilaxis.