This study will include patients aged between 18 and 70 who will undergo retrograde intrarenal surgery (RIRS) due to renal stone(s). A total of 80 patients (male or female) will be recruited, and will be randomized into 2 groups consisting of 40 patients in each group. The first group of patients will undergo RIRS with a ureteral access sheath (UAS) positioned prior to surgery; and the second group will undergo RIRS without UAS. As use of UAS decreases the pressure in the renal pelvis during RIRS, it is aimed to evaluate whether using UAS or not affects the level of pain felt by patients in the postoperative period.