Renal and ureteral temperatures changes during ureteroscopic pulsed thulium: YAG laser lithotripsy: an in vitro analysis.

Introduction: Promising studies have shown a high stone-free rate achieved with the pulsed solid-state thulium YAG laser. However, studies on its safety concerning temperature effects during activation remain limited. The aim of this study was to characterize temperature variations during laser activation.

Material and methods: This in vitro experimental study utilized a high-fidelity uretero-renal simulation model to assess temperature changes during intracorporeal laser lithotripsy. Temperatures reached after laser activation at 15, 20, and 30 seconds were recorded. The flow rates used were 10 ml/min and 20 ml/min. The maximum allowed temperature was set at 43°C, given its association with thermal tissue damage. A linear logistic regression model was used to analyze variations and project temperature behavior over time.

Results: In the renal model, temperature increases were correlated with the applied energy. With a 10 ml/min flow rate, no laser configuration exceeded 43°C at 15 seconds; at 20 seconds, only the 30 W (2.5 J/20 Hz) configuration exceeded this temperature. By 30 seconds, all 30 W configurations exceeded 43°C, except for 0.4 J/75 Hz. With a 20 ml/min flow rate, no laser configuration exceeded 43°C. The 20 ml/min flow rate decreased renal temperature by 1.96°C (p = 0.01). In the ureteral model, the temperature increase was not proportional to the applied energy, but in no scenario the temperatures reach the 43°C.

Conclusions: The temperature variations observed in this study with the use of the pulsed solid-state thulium YAG laser should be considered to avoid potential renal and ureteral thermal damage.