Objective assessment of working tool impact on irrigation flow and visibility in flexible ureterorenoscopes

Abstract

Background and purpose: Impaired irrigation causes reduced visibility in flexible ureteroscopy. The aim of this ex-vivo study was to investigate the impact of working tools on light transmission in a medium as an objective measurement of visibility in flexible ureteroscopes.

Materials and methods: Five ureteroscopes (Viper, Cobra, FlexX(2), URF-P5, DUR-8 Elite) were evaluated. The endoscopes were placed into a dark chamber with a photo diode, measuring light transmission. Light transmission was measured in a clear liquid and a 2% ink solution to simulate impaired vision. The time needed to restore light transmission by clear irrigation inflow was measured. Measurements were carried out five times, with empty and loaded ureteroscopes (1.7F, 2.2F basket, 273 μm laser fiber).

Results: The time needed to restore light transmission as a measurement of visibility depends on tool size and the length of the working channel. The presented setup provides more sensitive results than the measurement of the irrigation flow rate. With empty working channels, the fastest restoration of light transmission (increase by 1000 units) was achieved with the Cobra dual channel device (25 s), followed by single channel DUR-8 (28 s), Viper (38.5), and Flex X(2) (40 s). The ureteroscope with the longest working channel (URF-P5) needed the longest irrigation time to restore light transmission (66.5 s). These results become even more obvious with the use of different working tools.

Conclusion: Measurement of light transmission is a sensitive tool to evaluate irrigation performance. Double irrigation is superior to single irrigation in terms of light transmission.