The primary aim of the study is to compare stone free rates following ureteroscopic (URS) lithotripsy for renal stones with Thulium Fiber Laser (TFL) using a sheathless approach (low power laser settings) or using a flexible and navigable ureteral access sheath (FANS) with either low power or high power laser settings. Secondary aims are to compare the results of sheathless- and FANS assisted URS lithotripsy in terms of operative time, laser time, intraoperative and postoperative complications. Following the primary comparison between sheathless and FANS groups, another aim is to compare the outcome of low power and high power URS lithotripsy in the FANS patients with respect to operative time, SFR, laser time, intraoperative and postoperative complications.

Patients ≥ 18 years with renal stones (8-25 mm) scheduled for URS lithotripsy at the Day Surgery Clinic at Haukeland University Hospital in Bergen, Akershus University Hospital and The Hospital of Vestfold - all renal stone centres in Norway, are eligible for inclusion in the study. After written consent and inclusion, patients are randomised to laser lithotripsy using one of three alternative ureteroscopic approaches: Group 1: Sheathless URS using low power TFL 4 -10 Watts, short pulse mode, Group 2: URS with FANS using low power TFL 4 - 10 Watts, short pulse mode or Group 3: URS with FANS using high power TFL 16 - 24 Watts, short pulse mode. The ureteroscopic procedures are performed in general anaesthesia using a standardised technique. All patients are followed up with a low dose CT scan 3 months post endoscopically to assess stone free status as well as a consultation at the outpatient clinic. Results and data for the three randomisation groups are compared according to the aims of the study.