Experimental stone clearance with in-scope suction and flexible and navigable suction access sheaths

To perform benchtop experiments using direct in-scope suction (DISS) ureteroscopes (Pusen Medical, Zhuhai, China; 3.6-Ch and 5.1-Ch working channels) and flexible and navigable suction (FANS) ureteric access sheaths (ClearPetra; Wellead, Guangzhou, China) to establish their ability to clear stones of different diameters.

For each experimental group, we conducted a series of experiments using mixes of progressively larger stone particles (<63, 63-125, 125-250, 250-500, 500-1000 and 1000-2000 μm) until suction through the respective lumen failed to achieve complete stone clearance; the first experiment's stone mix contained particles <63 μm; the second experiment's stone mix contained particles <63 μm + 63-125 μm; the third experiment's stone mix contained particles <63 μm + 63-125 μm + 125-250 μm, and so on, up to 2000 μm. The stone mixes were introduced in aliquots over the course of 30 min. In the first experimental group, either a 3.6-Ch or a 5.1-Ch working channel DISS ureteroscope (with a 200-μm laser) was used to aspirate stones. In the second experimental group, either an empty 5.1-Ch working channel DISS ureteroscope or an 11/13-Ch FANS with a 9.5-Ch ureteroscope (intermittently withdrawn) was used to aspirate stones.

The use of DISS through a 3.6-Ch working channel (with laser fibre) cleared stones up to 250 μm. DISS through a 5.1-Ch working channel cleared stones up to 500 μm with and without an indwelling laser fibre. FANS cleared all stone sizes tested (up to 2000 μm).

During laser lithotripsy, DISS can aspirate 'dust' particles (<250 μm), which are known to most affect vision. However, particles >250 μm and >500 μm (with 3.6-Ch and 5.1-Ch working channels) may block the ureteroscope. The use of FANS, through successful clearance of larger fragments, may facilitate clearance of larger fragments.