New ureteral access sheaths: a double standard

To investigate the functional characteristics of the traditional and new single-wire ureteral access sheath (UAS) configurations relating to insertion, positioning, tissue injury, and durability.

Four UAS were tested: Navigator HD (11/13F, Boston Scientific), Re-Trace (10/12F, Coloplast), Flexor-Parallel (P), and Flexor-Regular (R; 9.5/11.5F, Cook Medical). UASs were evaluated for sharpness-(1) foil perforation, (2) tissue skiving (advancing sheath/dilator against fixed foil or bologna models); rigidity-(3) tip bending, (4) sheath buckling; (5) lubricity (dynamic friction through bologna), (6) dilator removal force, (7) kinking forces (side wall compressive forces), and (8) radiopacity. New UASs were used for each trial. A motorized sliding stage was used, and continuous force measurements were recorded with a Mark-10 digital force gauge.

The Navigator HD had the largest external diameter (13.02F). Re-Trace had the longest (51 mm) and most flexible tip (0.942 lb, P <.001). Flexor-R had the shortest (23.2 mm) and stiffest tip (7.48 lb). The Cook tip perforation forces were highest (0.807 lb), whereas the sheath required the most force (0.25 lb, P <.001) and caused the least damage (4.95 mm) when advanced against tissue. Navigator HD had the least frictional resistance (0.14 lb, P <.001). The single-wire systems had the lowest buckling forces (Navigator HD, 0.41 lb; Flexor-R, 0.827 lb; Flexor-P, 0.445 lb; Re-Trace, 1.014 lb; P <.001) and the highest dilator removal forces compared with classic systems (Flexor-P, 1.39 lb; Re-Trace, 1.9 lb; Navigator HD, 0.190 lb; Flexor-R, 0.194 lb; P <.001). The differences in kinking forces and radiopacity were not significant.

The Navigator HD was the most slippery and rigid sheath, whereas the single-wire systems had lower buckling forces and required more force to remove their dilators. Cook sheaths appeared the least traumatic.