Comparison of laser fiber passage in ureteroscopic maximum deflection and their influence on deflection and irrigation: Do we really need the ball tip concept?

PURPOSE: To examine laser fiber passage capabilities through flexible ureterorenoscopes (fURSs) and to measure deflections and flow characteristics.
METHODS: For this in vitro study, eight fURSs were examined (Olympus® URF-P6, URF-P6, URF-V, URF-V2; Storz® Xc and Flex-X2; Richard Wolf® Cobra Vision; and Lithovue). Four laser fibers standard 200- and 273-μm (uncleaved and cleaved), sheath-coated and ball-tip fibers were attempted to pass through each fURS while deflected at 120°, 180°, maximum deflection, and maximum deflection with reduced 9-mm radius. Measurements included maximal (up/down) deflections and irrigation flow rates achieved with each fiber.
RESULTS: Wolf Cobra Vision demonstrated minimal loss of deflections with mean differences of -2°/0° (p > 0.05) when loaded with the 200-μm fiber. The 273-μm fiber provoked utmost deflections that decline when loaded in Olympus URF-P5: mean differences of -52°/-35° (p < 0.001 for upward deflection). Of overall deflections, sheath-coated fiber induced least insult (p > 0.05), while standard 273-μm fiber incited maximum degradation (p < 0.00001). With few exceptions, sheath-coated and ball-tip fibers passed through all maximally deflected scopes. Uncleaved 200- and 273-μm fibers failed to pass through most maximally deflected fURS. However, cleaving their ends allowed 200- and 273-μm fiber to pass through all angles of deflections expect in the Olympus URF-P5 and Olympus URF-P5 and URF-V, respectively. The irrigation through all fURSs was significantly impaired (p < 0.00001).
CONCLUSIONS: fURS deflection was least affected by sheath-coated fibers and most affected by the 273-μm fiber. Uncleaved 200- and 273-μm fibers showed least passage capabilities; while removing the ends, the fibers greatly facilitated their passage capabilities as much as the other fibers tested.