Evaluation of the effect of 100U of Onabotulinum toxin A on detrusor contractility in women with idiopathic OAB: A multicentre prospective study

AIMS: Intradetrusor injection of Onabotulinum Toxin A (BTX‐A) is a third‐line treatment for overactive bladder (OAB). Voiding dysfunction and the need for intermittent catheterization are potential complications, consequent to bladder contractility (BC) decrement. Primary aim: to evaluate BC variation after BTX‐A detrusor injection in women with idiopathic OAB. METHODS: A prospective multi‐institutional observational study was conducted. Medical history, bladder diary, 24‐h pad test, and invasive urodynamic parameters were recorded before and 4–6 weeks after BTX‐A 100U administration. BC was measured as Modified Projected Isovolumetric Pressure (PIP1), that is, maximum flow rate (Qmax) + detrusor pressure at Qmax (PdetQmax). Continuous variables were expressed as median and interquartile range. We compared continuous variables using Wilcoxon test and proportions between two times with Fisher exact test. RESULTS: No changes in PIP1 were observed (p > 0.05) in 45 women enrolled between January 2018 and September 2019. Median age was 54.6 years. At baseline, 91.1% had urge urinary incontinence, with 4.9 ± 2.6 daily pads used and a 24‐h pad test of 205.4 ± 70.8 g. Baseline detrusor contractility was normal in all the patients. Postoperatively, an improvement in the 24‐h pad test (p < 0.01), daily voids (p < 0.01), and nocturia (p < 0.01) occurred. Urodynamics pointed out a significant reduction of detrusor overactivity rate (p < 0.01) and an increase of median maximum cystometric capacity (p < 0.01). No difference was observed in median Qmax (p > 0.05), PdetQmax (p > 0.05), and PVR (p > 0.05). No patient needed postoperative catheterization. CONCLUSIONS: The current series provides evidence that detrusor injection of botulinum toxin is an effective option for treating OAB, without causing voiding dysfunction and BC impairment.