Detrusor underactivity (DU) with chronic urinary retention (CUR) remains a therapeutic challenge in urology. No pharmacologic therapy reliably restores bladder contractility. Surgical approaches such as transurethral bladder neck incision (TUI) aims to reduce outlet resistance, but reported outcomes are inconsistent, while botulinum toxin injection often provides only short-term benefit. Consequently, many patients remain dependent on clean intermittent catheterization (CIC) or long-term indwelling catheters, both of which significantly impair quality of life.
To address this unmet need, we previously introduced a combined approach: external urethral sphincter botulinum toxin A (BoNT-A) injection together with transurethral incision of the bladder neck (TUI-BN). This approach aims to reduce both functional sphincter overactivity and fixed outlet resistance to help patients void spontaneously. Our previous short-term results showed improved voiding efficiency and lower post-void residual urine, but the long-term effect remains unclear.
BoNT-A monotherapy usually requires reinjection every 3–7 months. Therefore, we conducted a one-year follow-up study to evaluate whether this combined treatment can maintain spontaneous voiding, reduce the need for repeated BoNT-A injections, and provide sustained improvement compared with bladder neck incision, BoNT-A injection or intravesical electrical stimulation alone.

We prospectively enrolled 15 women diagnosed with underactive bladder (UAB) and chronic urinary retention. All participants underwent a combined procedure of TUI-BN and ultrasound-guided BoNT-A (100U) injection into the external sphincter. Functional outcomes and symptom scores were evaluated at 3-, 6-, and 12-months post-operation. To analyze longitudinal changes, Generalized Estimating Equations (GEE) with a Gaussian distribution and identity link were employed. GEE was preferred over linear regression because it effectively handles the statistical dependency of data within the same individual over time, ensuring more robust and accurate parameter estimates for evaluating treatment trajectories. A p-value of < 0.05 was considered statistically significant.

At the 12-month follow-up, significant improvements were sustained across all primary endpoints. The mean post-void residual (PVR) decreased from 350 to 108.9 ml (p < 0.01), while voiding efficiency (VE) increased from 26% to 70.8% (p < 0.01). Total AUA symptom scores improved from 25.9 to 8.9 (p < 0.01), and the proportion of patients requiring clean intermittent catheterization (CIC) declined from 73.3% to 13.3% (p < 0.01).

Compared with reported outcomes for BoNT-A monotherapy, this combined approach showed better durability, with a lower repeated injection rate (26.7% vs 71%) and a longer therapeutic interval (8.3 vs 3.7 months). The observed gain in VE (44.8%) and improvement in AUA-QOL (-4.1) were also favorable compared with outcomes reported for intravesical electrical stimulation and TUI-BN monotherapy.

Combined TUI-BN and BoNT-A injection provides a durable one-year treatment option for UAB. This synergistic strategy effectively reduces catheter dependency and maintains improved voiding efficiency compared with monotherapies. These results support the sustained efficacy and long-term stability of this multi-modal approach in managing chronic urinary retention over a twelve-month period.

Huang, W. C., Tsai, C. Y., & Chou, E. C. (2024). An Alternative Approach for Treating Female Underactive Bladders with Chronic Urine Retention: A Pilot Study on Combined Transvaginal Ultrasound-Guided Botulinum Toxin A External Sphincter Injection and Transurethral Incision of the Bladder Neck. Toxins, 16(10), 441. https://doi.org/10.3390/toxins16100441
Liao, L., Deng, H., Chen, G., Chen, H., Huang, M., Xie, K., Wei, X., Xu, Z., Huang, B., Chong, T., Chen, Q., Xiao, H., Huang, Z., Jiang, H., & Jing, H. (2023). Randomized controlled trial of intravesical electrical stimulation for underactive bladder. BJU international, 131(3), 321–329. https://doi.org/10.1111/bju.15885
Wright, S. L., Ananthavarathan, P., Simeoni, S., Malladi, P., Pakzad, M., & Panicker, J. N. (2024). Long-term Outcomes of Periurethral Sphincter Botulinum Toxin in Female Chronic Urinary Retention. International neurourology journal, 28(3), 207–214. https://doi.org/10.5213/inj.2448176.088

Continence 19S (2026) 102617
DOI: 10.1016/j.cont.2026.102617