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.

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