A multicentric non-randomized prospective observational study on the clinical efficiency of thulium fibre laser in large volume stones (> 1000mm3).

Abstract

Our objective was to analyse the clinical efficiency of TFL in large volume stones during retrograde intrarenal surgery. Patients with large volume renal stones (> 1000mm3) 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 3months 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 (> 1000mm3), as less energy is required to ablate every mm3 of stone.