Effects of Endourologic Devices and Connectors on Irrigation Flow Through the Flexible Ureteroscope Working Channel

To evaluate the effect of different connector types and commonly used endourologic devices on irrigation fluid flow through the working channel of a flexible ureteroscope.

Irrigation flow was measured under a 200-cm H₂O pressure head using three connector types (Tuohy-Borst, UroLok, and Check-Flo) and a standard Y-set connection. Instruments tested included Piranha biopsy forceps, Segura hemisphere basket, Glidewire guidewire, and two laser fibers (200 μm and 365 μm). Each condition was repeated six times. Descriptive statistics were calculated, and one-way ANOVA was used to assess differences between groups.

With an empty channel, the standard Y-set connection achieved the highest mean flow (115.8 ± 4.3 mL/min), followed by Tuohy-Borst (113.0 ± 1.6), UroLok (100.2 ± 1.3), and Check-Flo (80.4 ± 0.5) (p < 0.001). Inserting instruments markedly reduced flow. The Piranha forceps and Glidewire guidewire produced the largest reduction (∼96-97%). A larger instrument diameter or the absence of a smooth coating significantly reduced flow across all connectors. With small-caliber instruments, connector design played a greater role: relative flow reduction was greatest with Tuohy-Borst (50.6%) and lowest with Check-Flo (38.0%). In absolute terms, UroLok yielded the highest median flow with laser fibers (38.7 mL/min), followed by Tuohy-Borst (37.5 mL/min) and Check-Flo (34.7 mL/min).

Both connector choice and instrument size significantly affect irrigation flow in flexible ureteroscopy. Large-diameter instruments almost abolish flow regardless of connector, whereas with smaller instruments, connector design influences performance. These findings emphasize the importance of selecting optimal connector-instrument combinations to maintain intraoperative visibility.