Flexible Endoscope Deflectability: Changes Using a Variety of Working Instruments and Laser Fibers

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Abstract
To measure the effects of different working instruments and holmium laser fibers on the deflectability in a variety of actively deflectable flexible endoscopes, a benchtop study was performed. The endoscopes studied were the Storz 7.5 flexible ureteroscope, the AUR-7 and AUR-9 flexible ureteroscopes (Circon-ACMI), a prototype Mitsubishi flexible ureteroscope (Mitsubishi Optics, Inc.), the ACN flexible cystoscope (Circon-ACMI), and the Storz flexible cystoscope. Working instruments included 1.6F (Wolf) and 1.9F (Microvasive) electrohydraulic lithotripsy (EHL) probes, 1.9F two-prong graspers and Bagley baskets, 2.4F Segura and helical baskets (Microvasive), 3.0F Segura basket, and 200- and 365-μm holmium laser fibers (Xintec). In ureteroscopes, the effect of 1.6F and 1.9F EHL probes ranged from having no effect in the Xintec 6,000, to decreasing deflection by 30° in the AUR-7. Working instruments that were 2.4F or greater reduced deflection from 33° to 93°. Better deflectability was noted with the 200-μm holmium laser fiber than with the 365-μm fiber. The diameter of the working instrument did not affect deflectability as severely in cystoscopes. No significant differences in deflection existed between the 365-μm and 200-μm fibers in the flexible nephroscopes tested. In general, working instruments less than 2.4F and the 200-μm laser fiber have little effect on deflectability compared with working instruments 2.4F or larger and the 365-μm fiber. Flexible cystoscopes, with their larger working channels and stronger deflection cables, are affected less by working instrument diameter than are flexible ureteroscopes.