Predictive Factors for the Successful Outcome of Urethral Sphincter Injections of Botulinum Toxin A for Non-Neurogenic Dysfunctional Voiding in Women.

[PURPOSE] Dysfunctional voiding (DV) is not uncommon in women with non-neurogenic voiding dysfunction. Because of its unknown pathophysiology, effective and durable treatment is lacking. This study aimed to analyze the results of treatment and predictive factors for a successful outcome of botulinum toxin A (BoNT-A) treatment in female patients with DV.

[METHODS] In total, 66 women with DV confirmed by a videourodynamic study (VUDS) were treated with a BoNT-A injection into the urethral sphincter once (n = 33) or several times (n = 33). VUDS was performed before (baseline) and after the BoNT-A treatment. Patients with a global response assessment of the voiding condition of 2 or 3 and a voiding efficiency (VE) of >20% than baseline were considered to have a successful outcome. The baseline demographics, VUDS parameters, and VUDS DV subtypes were compared between the successful and failed groups. Predictive factors for a successful outcome were investigated by logistic regression analyses.

[RESULTS] Successful and failed outcomes were achieved in 27 (40.9%) and 39 (59.1%) women, respectively. After BoNT-A injections, the maximum flow rate (Qmax), voided volume, and VE all significantly increased, and the postvoid residual (PVR) was slightly improved. No significant difference in the number of injections and medical comorbidity was found between the groups. However, the successful group had a higher incidence of previous pelvic surgery. No significant difference in the treatment outcome was found among patients with different urethral obstruction sites. Significant improvements in Qmax, voided volume, PVR, VE, and the bladder outlet obstruction (BOO) index were noted in the successful group. A lower VE at baseline and a history of surgery were identified as predictive factors for a successful outcome of BoNT-A injections for treating DV.

[CONCLUSION] BoNT-A injections into the urethral sphincter can effectively improve VE in 40.9% of women with DV. Women with higher BOO grades and previous pelvic surgery are predicted to have a successful treatment outcome.