The mineral composition of the 437 urinary stones was studied in 437 patients with urolithiasis aged from 16 to 75 years, which have been treated in the National Scientific Urological Institute. Body-mass index (BMI), blood biochemistry panel and biochemistry of 24-hour urine probe were evaluated in all patients. Quartile analysis of the data was done according to the BMI distribution. Lower quartile was represented by BMI values < 24.1 kg/m2 (n=99), upper quartile by BMI values > 33.1 kg/m2 (n=99). The patients with urolithiasis and obesity compared to those without obesity presented with increased excretion rates of uric acid (1.15 times more, p< 0.006), phosphates (1.18, p< 0.01), lower pH level (p< 0.025). The patients with higher BMI conferred in stone composition more uric acid and less carbon apatite, when compared to patients with lower BMI (р=0.0774, р=0.0654, correspondingly). In patients with obesity struvite concentration was 1.8 times higher (p=0.0302). 

The patients with urolithiasis and BMI higher than 33.1 kg/m2 compared to the patients with BMI lower than 24.1 kg/m2 carry a high risk of urate stones formation (OR 6.5, p< 0.0001), lower risk of phosphate stones formation from the carbon apatite (OR 0.252, p< 0.0001) and a increased propensity to the struvite stone formation (OR 2.84, p=0.056). 

Body mass normalization in patients with uric acid stones could be accounted for one of the main methods of effective prophylaxis of urate urolithiasis and its recurrences together with other methods of metaphylaxis.