Direct-in-scope suction with a 5.1Fr large working channel ureteroscope: what stone dust size for effective evacuation during laser lithotripsy? An in vitro analysis by PEARLS and section of EAU Endourology.

Abstract

Purpose: A novel larger 5.1Fr working channel flexible ureteroscope for Direct-In-Scope Suction (DISS) has recently been introduced. However, the optimal stone dust size for successful evacuation without working channel blockage is currently unknown.

Methods: In vitro assessment of the PU400A 9.2Fr ureteroscope (Zhuhai Pusen Medical Technology Co., Ltd, China) was performed with BegoStone particle sizes ≤ 2000 μm (size range 1000-2000 μm), ≤ 1000 μm (500-1000 μm), ≤ 500 μm (250-500 μm), ≤ 250 μm (125-250 μm) and ≤ 125 μm (63-125 μm), in a kidney calyx model. This was conducted with an empty working channel, and with occupancy by 150 μm Olympus, 200 μm Quanta, 270 μm Dornier laser fibers. Primary outcome was complete suction-evacuation without working channel blockage. Secondary outcome was evacuation speed for particle sizes that did not have blockage.

Results: A stone particle size upper limit of 250 μm was found to achieve complete suction-evacuation without blockage, across all working channel occupancy situations. For stone particle size of range 125-250 μm, evacuation speeds were 35, 26, 13, 11 mm³/s across empty, 150 μm Olympus, 200 μm Quanta, 270 μm Dornier laser fiber occupancy, respectively (ANOVA = p < 0.001). For stone particle size range 63-125 μm, evacuation speeds were 19, 14, 9, 8 mm³/s respectively (ANOVA = p < 0.001).

Conclusion: The 5.1Fr working channel DISS ureteroscope allows a stone particle size limit of 250 μm to be suction-evacuated without blockage, even with laser fiber occupancy. With a laser fiber, a smaller 150 μm fiber size allows better particle evacuation speeds. Urologists should therefore aim for a dust particle size of ≤ 250 μm in routine DISS with the 5.1Fr working channel ureteroscope, for effective intraoperative stone evacuation.