Thermal safety during retrograde intrarenal surgery and laser lithotripsy. Changes of intrarenal temperature while using direct-in-scope-suction : an in-vitro study by young academic urologists and EAU endourology sections.

purposeTo evaluate the intrarenal temperature (IRT) variations using the 9.2Fr and 7.5Fr flexible ureteroscopes featuring direct-in-scope suction (DISS-FURS) in an in-vitro set up in different inflow and outflow irrigation conditions. MATERIALS AND

methodsThe experimental setting consisted of two DISS-FURS: a 7.5Fr ureteroscope with a 3.6Fr working channel (WC), and a 9.2Fr scope with a 5.1Fr WC. An Aldaver upper urinary tract model was used, and IRT was continuously monitored using a calibrated digital thermometer. Temperature dynamics were assessed by measuring the time required for IRT to increase from physiological baseline (37 °C) to 43 °C, from 43 to 50 °C, and the time required for IRT to decrease from 50 °C to 43 °C and to 37 °C following laser deactivation. Measurements were performed using a 272-µm laser fiber. A Holmium: YAG laser was activated continuously at power settings of 10 and 20 W. Experiments were conducted under the following conditions: with/without ureteral access sheath (UAS), with gravity-driven irrigation alone, with manual pump-assisted irrigation, and with/without activation of the DISS system. Thermal dose was calculated using the cumulative equivalent minutes at 43 °C (CEM43). A total of 32 experimental cohorts (96 experiments) were analyzed.

resultsFor the 7.5Fr DISS FURS, the safest combinations, defined by slower IRT rise and more controlled thermal profiles, were those with manual pump-assisted irrigation, use of UAS and no DISS activation. IRT increased more rapidly at 20 W in cohorts combining DISS activation without manual pump assistance and without UAS. In experiments performed with the 9.2Fr DISS FURS, manual pump-assisted irrigation and the use of UAS represented the safest maneuver for maintaining controlled IRT levels. The larger 5.1Fr WC allowed increased inflow, prolonging the time to critical temperature thresholds even when DISS was activated.

conclusionsThe combination of manual pump-assisted irrigation, UAS use, and the 9.2 Fr DISS flexible ureteroscope with a 5.1 Fr working channel provided the most favorable intrarenal temperature profile. In contrast, simultaneous activation of suction and laser with the smaller 7.5Fr scope, particularly without adequate irrigation, may increase thermal risk and should be used with caution. These findings suggest that optimizing irrigation dynamics and coordinating suction use are key to minimizing thermal risks during DISS-assisted FURS. Further clinical studies are warranted.