Irrigation performance of a 2-mm rigid cystoscope designed for neonatal cystoscopy: a bench study.

PURPOSE: Neonatal and infant cystoscopy is limited by narrow urethral caliber and the lack of sufficiently small cystoscopes with adequate irrigation. We developed a 2-mm (6 Fr) rigid cystoscope prototype and evaluated irrigation performance in a benchtop open-flow system. METHODS: The prototype incorporated a 0.9-mm optical channel, a 0.7-mm working channel, and two irrigation lumens (0.48 mm each). Irrigation performance was assessed under gravity and cuff-assisted irrigation, including temperature-controlled experiments. The maximum cuff pressure of 300 mmHg was used as an upper-bound bench condition and was not intended to represent a recommended clinical setting. Outflow was measured gravimetrically, and mean flow was calculated over 60 s. RESULTS: Gravity irrigation yielded 2.12-8.50 mL/min. Cuff-assisted irrigation increased flow from 17.39 mL/min at 150 mmHg to 40.40 mL/min at 300 mmHg (p < 0.001). At 300 mmHg, warming saline from 20 °C to 37 °C increased flow from 27.49 to 40.40 mL/min (p < 0.001). Probe insertion reduced flow by 4.4% (p = 0.157). CONCLUSION: The 2-mm rigid cystoscope achieved flows up to 40.4 mL/min, within the benchmark range adopted for this benchtop evaluation. These findings support benchtop technical feasibility of the irrigation design. Clinical safety and recommended irrigation pressures remain to be established in closed-system and in vivo studies.