Transurethral incision of congenital obstructive lesions in the posterior urethra in boys and its effect on urinary incontinence and urodynamic study
Authors: Nakamura Shigeru , Kawai Shina , Kubo Taro , Kihara Toshiharu , Mori Kenichi , Nakai Hideo 
Published: August 2010

Study Type – Therapy (case series) Level of Evidence 4

What’s known on the subject? and What does the study add?

We have clarified that there exist two types of voiding urodynamics (pressure‐flow‐study) for congenital urethral obstruction in boys; one is synergic pattern (SP) and the other is dyssynergic pattern (DP). In terms of daytime incontinence and nocturnal enuresis, the transurethral endoscopic incision of these obstructive lesions is only effective in the SP type, while never effective in the DP type. The synergic pattern (SP) seems to represent simple anatomical obstruction, while the dyssynergic pattern (DP) may represent anatomical obstruction complicated with functional obstruction.

The efficacy of endoscopic incision to mild forms of congenital urethral obstruction has been controversial, especially in terms of nocturnal enuresis. One of the reasons for the controversy is due to the lack of pre‐and post‐operative urodynamic assessment with its linkage to symptomatic change. We have, for the first time in the world, systematically conducted voiding urodynamic study for those elusive lesions seen in enuretic boys. Conclusively, for simple mechanical obstruction (SP), we confirmed that some voiding urodynamic parameters improve after the endoscopic incision, parallel to symptomatic improvement, while in the rest (DP) endoscopic incision is never effective. The cause of this ineffectiveness seemed to be due to persistent functional obstruction having superimposed on mechanical obstruction. The result of the study urges us to be more keen to diagnose and treat the mild congenial urethral obstruction as well as the concomitant functional obstruction in boys with nocturnal enuresis.

OBJECTIVE

• To evaluate the clinical significance of congenital obstructive lesions of the posterior urethra in boys with refractory primary nocturnal enuresis.

PATIENTS AND METHODS

• VCUG was performed in 43 consecutive boys who visited our department from April 2004 to April 2009 who were unresponsive to conservative treatment. 20 patients of the 43 patients, underwent TUI. VCUG and UDS were performed before and 3–4 months after TUI.

• In UDS, the maximum flow rate (Qmax), maximum bladder capacity, and post‐voiding residual urine volume were determined using uroflowmetry (UFM), and the detrusor pressure (Pdet) at Qmax was determined in a pressure flow study (PFS).

• Clinical outcome was evaluated 3–4 months and 6 months after TUI.

RESULTS

• In VCUG performed 3–4 months after TUI, improvement was observed in urethral morphology in all patients. In preoperative PFS, two patterns were observed: 13 patients (65%) had a synergic pattern (SP) in which the Pdet increased with increasing urinary flow rate simultaneously with the initiation of voiding and seven (35%) had a dyssynergic pattern (DP) in which the Pdet was not coincident with the initiation of voiding, but was higher immediately before voiding than at Qmax. TUI was effective only in the SP group: symptomatic improvement was observed in 87.5% of patients with daytime incontinence and 77% of patients with nocturnal enuresis 6 months after TUI.

• In the DP group, no effect was observed (0%). With regard to changes in UDS parameters, a significant decrease (P= 0.0004) was observed in the Pdet at Qmax and a significant increase (P= 0.036) was observed in the maximum bladder capacity in the SP group, whereas no significant differences were noted in any parameters in the DP group.

CONCLUSION

• Two voiding urodynamic patterns with different clinical outcomes of TUI were detected among patients with congenital posterior urethral obstruction, the underlying disease of refractory primary nocturnal enuresis in boys.