It’s Getting Hot in There: In Vitro Study on Ureteral Tissue Thermal Profiles During Laser Ureteral Lithotripsy

Introduction: The integration of laser technology in urologic interventions, especially ureteral lithotripsy, has greatly advanced the field, with laser lithotripsy becoming the preferred method for treating ureteric stones via ureteroscopy. Recent advancements focus on enhancing power settings and reducing operating times, introducing high-power laser equipment capable of frequencies up to 120 Hz. However, concerns arise regarding thermal injuries to adjacent tissues due to increased energy delivery, potentially causing ureteric strictures. Objective: To explore temperature dynamics during ureteroscopic laser lithotripsy, considering factors like laser power settings and ureteroscope size, to optimize outcomes and mitigate risks for patients. Methods: A simulated in vitro model for ureteroscopic laser lithotripsy was designed with a holmium laser. Measurements of the temperature were recorded using a thermocouple placed at the laser tip at different sizes of ureteroscope (URS 6.0 Fr and URS 7.0 Fr), holmium laser (272 µm and 365 µm), various power settings (5 to 25 Hz; 0.2 to 3.0 J) and activation durations (3 to 30 s). Analysis of the variables associated with temperature change was performed. Results: All of the variables showed rising temperature trends as the laser activation time was prolonged, while ureteroscope size had no significant impact. Smaller laser fibers exhibited lower overall temperature profiles, around 34–35 °C. Notably, power settings significantly influenced temperature, with a substantial rise at 20 W (42.62 °C) and 30 W (40.02 °C). There was a significant rise in temperature as power (J × Hz) increased, where frequency carries a higher effect than energy at the same power setting. Conclusions: The recommendation includes exercising caution with higher power levels, shorter activation times, and preferably using small-caliber laser fibers to maintain lower temperatures.