Purpose: Endoscopic transurethral incision (TUI) of posterior urethral valve (PUV) can improve daytime urinary incontinence (DUI) and nocturnal enuresis (NE). However, the underlying mechanism has not been elucidated. In this study, we retrospectively examined the mobility of the urethra before and after TUI by measuring the urethral angle with voiding cystourethrography (VCUG), to clarify the effects of TUI on the morphology of the urethra during voiding.
Methods: Between July 2010 and December 2014, 29 boys with intractable DUI and/or NE were diagnosed as PUV and underwent endoscopic TUI. VCUG during voiding phase was performed at sequential radiographic spot images (1 image per second) at a 45° angle in oblique standing position. The point at which the angle of the urethra was the smallest during urination was regarded as the minimum urethral angle. The maximum urethral angle during early voiding phase was compared with the minimum urethral angle, and the percentage by which this angle changed was calculated as the flexion rate. Then changes in minimum urethral angle and flexion rate were analyzed before and 3-4 months after TUI.
Results: After TUI, the minimum urethral angle on VCUG became more obtuse (before vs. after TUI, respectively: 112.7 vs. 124.5°, p < 0.001), the flexion rate decreased (before vs. after TUI, respectively: 11.8 vs. 4.1%, p < 0.001).
Conclusions: This study demonstrated a significant difference in the degree of change. The findings may contribute to understanding of the mechanism of improvement in symptoms after TUI in patients with PUV.
Keywords: Posterior urethral valve; Transurethral incision; Urethral angle; Voiding cystourethrography.