Thermal injury and treatment efficiency during thulium fiber laser lithotripsy: insights from an in vivo porcine model.

PURPOSE: To evaluate the risk of thermal injury and the treatment efficiency during thulium fiber laser (TFL) lithotripsy of renal and ureteral stone phantoms in an in vivo porcine model.

METHODS

BegoStone phantoms were sequentially implanted and treated in the kidneys and ureters of five live anesthetized pigs using ureteroscopy and a 200-µm TFL fiber. Room-temperature saline irrigation (20 mL/min) was used. Intraluminal temperatures were monitored using thermocouples. Nine kidney stone treatments were performed at 0.8 J/12 Hz, 0.2 J/100 Hz, and 1 J/20 Hz. Twelve ureteral stone treatments were performed at 0.8 J/12 Hz, 2 J/5 Hz, 0.2 J/100 Hz, and 1 J/20 Hz. Treatment efficiency was assessed by measuring residual stone mass. Histopathological examinations assessed for thermal injury.

RESULTS

In kidney treatments, maximum temperatures were lower at 10 W settings (median 33.2˚C) than at 20 W (45.7˚C, p = 0.020). Histology revealed major thermal injury in 1/3 treatments at 10 W and 4/6 at 20 W (p = 0.524). In ureter treatments, temperatures did not differ significantly between 10 W (median 36.3˚C) and 20 W (44.6˚C, p = 0.109) settings. However, major histologic thermal injury occurred in 1/6 treatments at 10 W and 6/6 at 20 W (p = 0.015). Median treatment efficiency was 0.57 mg/sec (kidney) and 0.35 mg/sec (ureter), with no significant differences among settings.

CONCLUSION

TFL lithotripsy at 20 W can exceed thermal safety thresholds, especially in the ureter. Treatment at 10 W appears safer without significantly compromising efficiency, supporting its use for minimizing thermal injury risk.