Intraprocedural Pain During Intradetrusor Onabotulinum Toxin-A Injections: A Clinical Evaluation of Pain Distribution

This study aimed to evaluate the distribution and intensity of intraprocedural pain during intradetrusor onabotulinumtoxinA injections by assessing differences across anatomical bladder regions and diagnostic subgroups. Specifically, the study investigated whether pain perception varied based on gender, diagnosis, and injection site in patients with idiopathic detrusor overactivity (IDO), neurogenic detrusor overactivity (NDO), and wet overactive bladder (OAB-wet).

In this prospective observational study, 119 adult patients who underwent intradetrusor onabotulinumtoxinA injections between March 2021 and October 2023 were included. Patients were diagnosed with IDO, NDO, or OAB-wet. All procedures were performed using flexible cystoscopy under local anesthesia with Optilube gel. A standardized 20-site injection protocol was used, including two injections on each lateral wall, five in the para-trigonal region, and 11 in randomly distributed sites on the anterior and posterior bladder walls. Patients reported their pain scores for each region using a 0-10 visual analog scale (VAS). A control group of 50 patients undergoing diagnostic flexible cystoscopy provided baseline pain scores. Two-way ANOVA was used to assess differences in pain scores based on gender, diagnosis, and anatomical region.

A total of 119 patients (82 females, 37 males) were included, with 88 diagnosed with IDO, 28 with NDO, and 3 with OAB-wet. The mean overall VAS pain score during BoNT-A injections was 4.03 ± 1.21, compared to 1.76 ± 0.68 in 50 patients undergoing diagnostic flexible cystoscopy (p < 0.001). Among injection sites, mean scores were 3.78 for para-trigonal, 4.03 for lateral wall, and 3.11 for randomly distributed regions. Two-way ANOVA showed no significant differences in pain scores by gender or diagnosis, except for para-trigonal pain, which was higher in OAB-wet patients (p = 0.01). Excluding this subgroup, no significant difference remained between IDO and NDO (p = 0.06).

Intravesical onabotulinumtoxinA injections are generally well tolerated under local anesthesia, though para-trigonal injections may cause greater discomfort, particularly in patients with OAB-wet. While pain perception did not differ significantly by gender or diagnosis overall, region-specific sensitivity should be considered when planning injection techniques. These findings may help inform strategies to improve procedural comfort and support individualized treatment approaches.

This study was not registered as a clinical trial because it was a non-randomized, observational study without prospective assignment or intervention groups, consistent with ICMJE criteria.