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

To examine laser fiber passage capabilities through flexible ureterorenoscopes (fURSs) and to measure deflections and flow characteristics.

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.

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).

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.