Thulium fiber laser versus pulsed Thulium:YAG for laser lithotripsy during flexible ureteroscopy

To compare the pulsed-Thulium: YAG(p-Tm: YAG) and Thulium Fiber(TFL) lasers in terms of efficiency and safety profiles during flexible ureteroscopy(fURS) and endocorporeal laser lithotripsy(ELL). A prospective single-center open-label comparative study included consecutive patients with ureteral and renal stones who underwent fURS using Thulio(p-Tm: YAG, Dornier©,Germany) or TFL Drive(TFL, Coloplast©,Danemark), with 270 μm and 150/200μm laser fibers(LF), respectively. fURS were performed by a single operator in each group. Demographics, stone size, stone density, laser-on time(LOT) and laser settings were recorded. Ablation speed(mm³/s), energy consumption(J/mm³) values for each procedure were also assessed. Stone-free rate(SFR, <3 mm fragments) and zero fragment rate(ZFR) on non-contrast computed tomography within 3 months postoperatively were also recorded. 36 and 39 patients were included in p-Tm: YAG and TFL group, respectively. Groups presented similar demographics but for high blood pressure(53vs23%,p = 0,005), anatomical abnormalities(8vs33%,p = 0,03), lower pole(8vs26%,p = 0,04) and pelvic stones(25vs13%,p = 0,04) for p-Tm: YAG and TFL, respectively. The median stone maximum diameter was higher in the p-Tm: YAG group(17.3vs13.8 mm, p = 0,001) but stone volume was similar among groups(1514vs1347mm³,p = 0,6). Laser settings were similar among groups(0,6-15 Hz,10-12 W). Shorter LOT(< 0,001) and lower UAS insertion(0,01) rates were reported for TFL compared to p-Tm: YAG. The median J/mm³ was similar(14vs17,p = 0,2) but p-Tm: YAG presented higher ablation speed(0,91vs0,73mm³/s, p = 0,04). SFR were similar among groups(75vs77%,p = 0,8) but ZFR was higher in TFL group(39vs64%,p = 0,008). No difference in complications was reported. Both p-Tm: YAG and TFL are safe and effective for ELL during fURS. SFR were similar between TFL and p-Tm: YAG but the latter presented lower ZFR, traducing its lower ability to dust. Using 200 μm laser fibers with p-Tm: YAG could nuance these findings.