Flexible ureteroscopy using the novel 6.3 flexible ureteroscope. Does it affect the intrarenal fluid temperature? An in vivo experimental study.

Abstract

Objective: To evaluate intrarenal fluid temperature (IFT) changes during high-power Holmium:YAG (Ho: YAG) laser activation using a 6.3 Fr single-use ureteroscope in an in vivo porcine model replicating human anatomy.

Methods: Three female pigs underwent flexible ureteroscopy with and without ureteral access sheath (UAS), and with or without artificial stone presence. A 150 W Ho:YAG laser was applied at varying energy settings (10 W to 60 W) using a 200 μm fiber. IFT was recorded continuously for 30 s per condition using a thermocouple. A total of 192 measurements were analyzed, with 43 °C set as the thermal injury threshold.

Results: Across all configurations, IFT remained below 43 °C. Higher laser settings (40 W and 60 W) were associated with statistically significant IFT increases (P < .01), but without surpassing cytotoxic thresholds. The use of UAS consistently reduced IFT compared to conditions without a ureteral access sheath. The presence of stone slightly attenuated the temperature rise, potentially due to partial laser energy absorption. The 6.3 Fr ureteroscope demonstrated favorable safety across scenarios.

Conclusion: In this in vivo model simulating renal anatomy, high-power Ho:YAG lithotripsy with the 6.3 Fr single-use ureteroscope did not result in thermal injury. UAS use and proper irrigation remain essential to controlling IFT. Findings suggest that device miniaturization combined with procedural awareness can enhance safety during high-power lithotripsy. Further clinical validation is warranted.