[Comparative study of the efficacy and safety of a new generation of thulium fiber lasers for ureteroscopy and lithotripsy].

Introduction: The development and implementation in clinical practice of a 3rd generation thulium fiber laser with the possibility of computer control (modulation) of the shape, amplitude and pulse repetition rate opens up new possibilities for thulium fiber laser lithotripsy.

Aim: To carry out a comparative study of the efficacy and safety of thulium fiber laser lithotripsy using a of the 2nd (FiberLase U3) and 3rd generation devices (FiberLase U-MAX).

Materials And Methods: A total of 218 patients with solitary ureteral stones, who underwent to ureteroscopy with lithotripsy using 2nd and 3rd generation thulium fiber lasers (IRE-Polus, Russia) from January 2020 to May 2022 with the same peak power (500 W), laser settings of 1 joule, 10 Hz and with a laser fiber diameter of 365 m, were included in the prospective study. For lithotripsy using FiberLase U-MAX laser a new original modulated pulse, which was found and optimized in a preclinical study, was used. Depending on the laser, the patients were divided into 2 groups. In 111 patients, stone fragmentation was performed on FiberLase U3 (2nd generation), while 107 patients were undergone to lithotripsy on a new laser device FiberLase U-MAX (3rd generation). Stone size ranged from 6 mm to 28 mm (11+/-4 mm). The duration of procedure and lithotripsy, the quality of the endoscopic picture during fragmentation (from 0 to 3 points, 0-bad, 3-excellent), the frequency of retrograde migration of stones, as well as damage to ureteral mucosa (of 1-3 degrees) were evaluated.

Results: The time of lithotripsy was significantly lower in the group 2 than in the group 1 (12.3+/-4.6 vs. 24.7+/-6.2 min; p<0.05). The average quality of the endoscopic picture was significantly better in the group 2 (2.5+/-0.4 vs. 1.8+/-0.2 points; p<0.05). Clinically significant retrograde migration of stone or its fragments (the need for additional ESWL, flexible ureteroscopy) was noted in 16% vs. 8% of patients in group 1 and 2, respectively (p<0.05). Damage to ureteral mucosa of the 1st and 2nd degree due to laser exposure in the group 1 was noted in 24 (22%) and 8 (7%) cases, compared to 21 (20%) and 7 (7%) cases in group 2, respectively. Stone-free state was 84% in group 1 and 92% in group 2.

Conclusion: Modulation of the laser pulse shape allowed to improve endoscopic visibility, increase the speed of lithotripsy, reduce the frequency of retrograde stone migration without increasing the trauma to ureteral mucosa.