FANS vs Sheathless URS Lithotripsy - a Prospective, Randomised Clinical Trial

BACKGROUND: Ureteroscopic laserlithotripsy (URS) is the preferred treatment modality for renal stones up to 20 - 25 mm. Continous development recent years with thinner flexible endoscopes, more efficient lasers and auxiliary eqiupment has expanded indications for URS. A few years ago, we performed a randomised clinical trial comparing URS lithotripsy using Holmium:YAG laser and Thulium Fiber Laser (TFL). The results of the study favoured TFL lithotripsy. However, there is no consensus regarding optimal laser settings using TFL. To address this issue, we recently performed another randomised clinical trial comparing URS lithotripsy using low and high TFL settings. In that study, low power laser settings resulted in significantly higher stone free rates and lower complication rates compared to high power lithotripsy. It should be noted that a sheathless approach was used in both groups. The sheathless approach used in this study has been criticised as the newly introduced flexible and navigable ureteral access sheath may improve stone free rates and reduce infectious complications.

However, to date, there are no clinical randomised trials comparing a sheathless approach and URS with FANS using different laser settings for TFL to determine what is optimal regarding the clinical outcomes.

AIMS OF THE STUDY: The primary aim of the study is to compare the stone free rates following URS lithotripsy for renal stones with low power TFL using a sheathless approach and URS with FANS (with low and high power 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.

STUDY DESIGN: The study is planned as a multicenter prospective randomised clinical trial. All patients ≥ 18 years scheduled to URS lithotripsy for renal stones, 8-25 mm, at the day surgery unit at Haukeland University Hospital (HUH), Akershus University Hospital (AHUH) and The Hospital of Vestfold are invited to be enrolled in the study. After written informed consent, 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.

In total, 225 patients will be included in the study, 75 from each of the three stone centres. Among the 75 patients recruited from each hospital, 25 will be randomised to each of the three randomisation groups.