A Novel Template for Intravesical Botulinum Toxin Injection in Patients With Idiopathic Overactive Bladder: A Cohort Study

INTRODUCTION: The intravesical injection of onoabotulinum toxin A is a cornerstone in the management of overactive bladder. Traditionally, treatment involves 20 injection sites, avoiding the bladder trigone. Recent studies have shown that trigonal injections do not induce or increase vesicoureteral reflux. A novel injection template has recently been proposed, consisting of 10 injection sites: 2 in the trigone, 4 in the retrigonal area, and 4 in the bladder fundus. This study aims to compare the efficacy and safety of the traditional and the novel injection templates in patients with OAB symptoms. METHODS: An observational, analytical, and retrospective cohort study was conducted. Patients aged 18 years or older with idiopathic overactive bladder refractory to oral pharmacological treatment were included. All participants underwent intravesical injection of botulinum toxin at a urology center in Bogotá between January 2023 and December 2024. Patients without follow-up data were excluded. Two groups were compared: those treated with the traditional injection template and those treated with the novel template. The sample size was calculated as 70 patients per group. The primary outcome was efficacy, defined as improvement in urinary frequency, urgency, and incontinence symptoms 6 months after treatment. The secondary outcome was safety, defined as the occurrence of adverse events within 6 months of the injection. A descriptive analysis was performed using measures of central tendency and dispersion. Bivariate analysis was carried out using the Mann-Whitney and Chi-square tests. RESULTS: A total of 133 patients were included: 67 in Group 1 (novel template) and 66 in Group 2 (traditional template). The median age was 64 years, and 80.45% were women. No significant differences were found in sociodemographic variables or baseline symptoms between the two groups. The primary outcome showed a significant difference favoring Group 1, with overall symptom improvement (total + partial response) of 90.91% versus 75.76% for urinary urgency, 85.18% versus 68.51% for urinary frequency, and 94.6% versus 61.91% for urinary incontinence, respectively, for Groups 1 and 2. The overall incidence of adverse events was 11.28% (95% CI: 6.45-17.92), with no statistically significant difference between groups (p > 0.05). The most frequent events were urinary tract infection, pain, hematuria, and the need for clean intermittent catheterization (CIC). All events were mild and did not require hospitalization. DISCUSSION AND CONCLUSIONS: The 10-point injection template for botulinum toxin administration, which includes two trigonal sites, demonstrated greater effectiveness than the traditional template in improving symptoms of urgency, frequency, and incontinence. Although mild adverse events were observed, there were no significant differences between the two groups, and the overall incidence was lower than that reported in the literature. The new 10-point template represents an innovative, effective, safe, and practical alternative for intravesical botulinum toxin administration in patients with overactive bladder refractory to oral therapy.