A multicentric non-randomized prospective observational study on the clinical efficiency of thulium fibre laser in...

Our objective was to analyse the clinical efficiency of TFL in large volume stones during retrograde intrarenal surgery.

Patients with large volume renal stones (> 1000 mm³) operated at two different centres, from May 2020 to April 2021, were enrolled in this study. Retrograde intrarenal surgery was performed using 60W Superpulse thulium fibre laser™ (IPG Photonics, Russia). Demographic data, stone parameters, laser time, and total operating time were recorded, and laser efficacy (J/mm³) and ablation speed (mm³/s) were calculated. NCCT KUB was done at 3 months postoperatively to calculate stone-free rate.

A total of 76 patients were included and analysed in the study. Mean stone volume was 1753.12 ± 1245.81 (1169.27-2193.25) mm³, mean stone density was 1104.46 ± 313.09 (875.00-1317.00) HU, mean laser time was 537.79 ± 689.89 (21.00-1080.00) sec, mean operating time was 43.38 ± 12.96 (35.00-51.25) min, mean laser efficacy was 20.30 ± 15.5 (8.88-25.57) J/mm³, and mean ablation speed was 1.32 ± 0.7 (0.82-1.64) mm³/sec. A strong positive correlation was found between the stone volume and ablation speed (r = 0.659, p = 0.000), and a moderate negative correlation was found between the stone volume and laser efficacy (J/mm³) (r = - 0.392, p = 0.000). With increasing volume of the stone, J/mm³ decreased significantly and ablation speed increased significantly (p < 0.001). Complications occurred in 21.05% (16/76) patients, most of which were Clavien grades 1-2. Overall SFR is 96.05%.

Laser efficiency increases at higher stone volumes (> 1000 mm³), as less energy is required to ablate every mm³ of stone.