Thermal determinants during in situ lithotripsy of nonrelocatable impacted ureteral calculi using a flexible and navigable suction ureteral access sheath: an in vitro study.

PURPOSE: In situ lithotripsy may be unavoidable when impacted ureteral calculi cannot be safely relocated. This in vitro study aimed to identify the key determinants of intraluminal temperature elevation when using a flexible and navigable suction ureteral access sheath (FANS) in this setting.

METHODS

A standardized silicone-based in vitro urinary system model simulating impacted ureteral calculi was constructed. Real-time temperature monitoring was performed using an intelligent temperature-sensing flexible ureteroscope. Experiments were conducted using holmium: yttrium-aluminum-garnet (Ho: YAG) and thulium fiber laser (TFL) with varying laser settings, irrigation flow rates (50 and 100 mL/min), negative pressure suction levels (none, - 150 mmHg, - 262 mmHg), and sheath sizes (10F and 12.5F). Temperature changes were continuously recorded during 1-minute laser activation.

RESULTS

Irrigation flow rate and laser setting showed significant main effects on intraluminal temperature elevation during Ho: YAG lithotripsy (both P < 0.001), whereas sheath size and suction level showed no significant effects. During TFL lithotripsy, sheath size, suction level, irrigation flow rate, and laser setting were all significantly associated with temperature elevation (all P < 0.01), with irrigation flow rate and laser setting showing the largest effect sizes. Under the laser settings shared by both platforms, TFL produced significantly greater intraluminal temperature elevation than Ho: YAG (P < 0.001). For Ho: YAG, temperature elevation was particularly pronounced at the highest tested setting (1.5 J × 20 Hz), while increasing irrigation provided greater cooling at higher laser settings. During TFL lithotripsy, temperature elevation increased with increasing negative-pressure suction, with the - 262 mmHg condition showing significantly greater temperature elevation than the no-suction condition.

CONCLUSION

When in situ lithotripsy is unavoidable for nonrelocatable impacted ureteral calculi, laser setting and irrigation flow rate are major determinants of intraluminal temperature elevation. Under the settings shared by both platforms, TFL was associated with greater temperature elevation than Ho: YAG. Adequate irrigation is particularly important at higher laser settings, whereas stronger suction should not be assumed to provide additional thermal protection.