We aimed to compare the laser efficiency and clinical outcomes of two widely used systems—the holmium MOSESTM laser and the thulium fiber laser (TFL)—in the ureteroscopic management of 1-2 cm renal calculi.

In this ongoing randomized controlled trial (RCT), we included 71 patients who underwent flexible ureteroscopy (f-URS) for a solitary 1-2 cm kidney stone between August 2022 and July 2024 at our institution. Patients were randomized to undergo treatment with either the holmium MOSES™ laser or TFL. All patients had postoperative computed tomography (CT) scans at 1 month and 3 months. Patient demographics and stone parameters were recorded, including stone site, size, volume, and density. Intraoperative data were collected and analyzed, including total operative time, ureteroscopy time, lasing time, total energy delivered, and stone composition. We recorded the presence of residual stones and the percentage of stone volume reduction. Ablation efficiency was calculated by dividing the energy utilized (J) by the stone volume (mm3). The ablation speed was calculated by dividing the stone volume (mm3) by the lasing time (sec). Patients with a stone size of 0 cm were deemed stone-free.

The MOSESTM and TFL groups comprised 35 and 36 patients, respectively, with no significant differences in baseline patient demographics or stone characteristics between the cohorts. The two modalities had comparable total energy, laser time, efficacy, and ablation speeds. Ablation efficiency was 25.7 J/mm³ in the MOSESTM group and 30 J/mm³ in the TFL group (p=0.98). Additionally, ablation speed was 1.1 mm³/sec in the MOSESTM group and 0.89 mm³/sec in the TFL group (p=0.26). No differences were observed in stone-free or retreatment rates.

The MOSESTM and TFL laser systems demonstrate comparable efficacy for lithotripsy of renal calculi during f-URS, with neither technology showing a distinct clinical advantage.