Does Injection Number Matter? A Systematic Review and Meta-Analysis of Bladder Botox for Overactive Bladder.

INTRODUCTION AND HYPOTHESIS: Intravesical onabotulinumtoxin-A (BoNT-A) is an established treatment for overactive bladder (OAB). Although the FDA-approved standard regimen involves 20-injections, evidence suggests fewer injections may achieve comparable outcomes. OBJECTIVES: To systematically review studies comparing periprocedural outcomes of reduced-injection versus standard 20-injection BoNT-A techniques for OAB. STUDY DESIGN: PubMed, Scopus, and Embase were searched from their inception through 6/11/2026. Eligible studies included women undergoing in-office bladder BoNT-A (100 U) for OAB. The intervention was a reduced number of injections and the comparator was the 20-injection protocol. Outcomes included efficacy, pain during injection, urinary tract infections (UTI), and retention. Abstracts and full-text articles were doubly screened; accepted articles were doubly extracted. Study quality was assessed using GRADE criteria, ROB2, and ROBIN-I. Random-effects meta-analyses were performed to pool proportions and risk ratios. RESULTS: We screened 4066 abstracts, 139 full-text papers were assessed, leaving 16 studies (eight RCTs and three retrospective cohort studies, four prospective cohort study, and one case series) with 1393 patients. Most outcomes were supported by low- to high-quality evidence. Mean follow-up was 8.7 ± 4.3 weeks, and the reduced-injection groups received a mean of 7.3 ± 2.8 injection sites. Meta-analysis demonstrated no difference in efficacy between reduced- and standard-injection protocols (79% (95% CI 0.66-0.89); p = 0.16). Pain scores were not different between the reduced-injection group and the standard-injection group (mean difference 0 (95% CI 0.36-0.34); p = 0.23)). UTI (16% (95% CI 0.12-0.21); p = 0.427) and urinary retention (4% (95% CI 0.02-0.06); p = 0.591) adverse events did not vary between groups. CONCLUSIONS: Reduced-injection BoNT-A regimens provide efficacy and safety comparable to the 20-injection protocol, supporting a simplified approach to OAB treatment without compromising outcomes.