Flexible ureterorenoscopy and lithotripsy with pulsed thulium: YAG laser: a multicenter retrospective study.

INTRODUCTION

In vivo data on volumetric laser efficiency and clinical outcomes of the p-Tm: YAG laser from large multicenter cohorts remain limited. The present study aimed to evaluate the real-world in vivo volumetric ablation efficiency of the p-Tm: YAG laser during flexible ureterorenoscopy (FURS), with secondary assessment of clinical outcomes and safety in a multicenter cohort.

METHODS

We conducted a retrospective multicenter cohort study including adult patients (≥ 18 years) who underwent p-Tm: YAG-based FURS for ureteral and/or renal calculi at three tertiary referral centers between 2023 and 2025. Preoperative stone volume was quantified using manual three-dimensional CT segmentation. Laser-on time (LOT), total delivered energy, and laser settings were prospectively recorded. Volumetric ablation speed (mm³/s) and energy consumption (J/mm³) were calculated using standardized definitions based on segmented pre- and postoperative stone volumes in patients with postoperative non-contrast CT (NCCT). Stone-free rate (SFR) was assessed 1-3 months postoperatively using NCCT and classified as Grade A (no residual fragments), Grade B (residual fragments ≤ 2 mm), and Grade C (residual fragments ≤ 4 mm). In patients without postoperative NCCT, SFR was assessed by intraoperative endoscopic evaluation and analyzed separately.

RESULTS

Of 222 screened patients, 167 met the inclusion criteria. Median preoperative stone volume was 987 mm³ (IQR 329-3,124), and 47% of patients presented with multiple/complex stones. Median LOT was 21.4 min, and median total delivered energy was 12 kJ. In the 108 patients with paired volumetric data and postoperative NCCT, median ablation speed was 0.55 mm³/s (IQR 0.30-0.95), and median energy consumption was 13 J/mm³ (IQR 8-23). In this NCCT subgroup, SFR were 47%, 59%, and 66% for Grade A, B, and C, respectively. Among the 59 patients assessed endoscopically only, complete stone clearance was visually assessed in 20 patients (34%). Overall, 45 patients (27%) required additional stone-related treatment. Complications were uncommon, with 4.8% Clavien-Dindo grade I-II events and 0.6% grade III events; no grade IV-V complications were observed.

CONCLUSION

In this multicenter real-world cohort, p-Tm: YAG laser lithotripsy showed measurable volumetric efficiency and was associated with acceptable stone clearance and a favorable safety profile during FURS. These findings support the clinical feasibility of this technology in routine endourological practice; however, prospective comparative studies are warranted to further define its relative performance compared with established laser platforms.