GSTM1 and chronic kidney disease: Stratification of age, BMI, size of the stone, operative time, preoperative Hb level, stone surface area (in cm2), hypertension, diabetes mellitus, preoperative UTI, gender, staghorn stone, chronic renal failure, socioeconomic status, number of tracts, access calyx, dilation method, and side of puncture with blood transfusion was performed.