Abstract
OBJECTIVE: 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. METHODS: 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either an empty 5.1-Ch working channel DISS ureteroscope or an 11/13-Ch FANS with a 9.5-Ch ureteroscope (intermittently withdrawn) was used to aspirate stones. RESULTS: 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). CONCLUSIONS: 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.