Flexible ureteroscopes: a user's guide

To compare, quantitatively and qualitatively, four small-diameter flexible ureteroscopes.

Four flexible ureteroscopes from different manufacturers, i.e. the DUR-8 (ACMI, Southborough, MA, USA), Olympus UPF-3 (Keymed, Southend-on-Sea, UK), Storz 11274AA (Karl Storz GmbH, Tuttlingen, Germany) and the Wolf 9 F (Henke Sass Wolf GmbH, Tuttlingen, Germany), were assessed quantitatively by measuring the active tip deflection and irrigation flow rate with laser fibres (200 micro m, 365 micro m), an electrohydraulic lithotripter (1.9 F) and grasping forceps (3 F) in position. They were then assessed subjectively by two endourologists who scored them, using a visual analogue scale (maximum 10), for insertion, deflection mechanism, manoeuvrability, rigidity, image quality and overall satisfaction.

All the endoscopes are < 9 F at the tip, although the length of the smallest diameter (bevelled tip vs section of shaft) was variable. Tip deflection was 87-100% of the manufacturers' specifications and decreased by similar percentages with instruments in the working channel. The irrigation flow rate was comparable for instruments with a 3.6 F working channel (72-88 mL/min with an empty working channel), although much greater for the Wolf, which has a 4 F channel (116 mL/min). Direction and image size were nearly identical, as was the field of view, apart from the Wolf (60 degrees vs 90 degrees ). There was agreement in the user assessment for three instruments, with overall satisfaction scores being Storz (4), ACMI (7.5) and Olympus (8.6), but disagreement in scores for Wolf (1.9 vs 5.3).

Whilst there were considerable similarities in the objective assessment among the instruments, the user assessment showed qualitative variability. Thus it is important to try the different instruments before selecting one. Additional variables to consider include durability, cost and service/warranty, which vary considerably among instruments.