Bladder Wall Structure Alterations in Patients Treated With Botulinum Toxin for Detrusor Overactivity-A Morphological Study

Background/Aim: The overactive bladder syndrome (OAB) is a bothersome condition that affects up to 33% of the population. In up to 69% of the cases, the underlying condition is an overactive detrusor (DO). Treatment options rely on behavioral changes, medical treatment, neuromodulation, and invasive treatment, such as injecting botulinum toxin (BoNT) in the detrusor or augmentation cystoplasty. The aim of this study was to evaluate, by morphological assessment on cold-cup biopsies of the bladder, the effect of botulinum toxin injections on the bladder wall, focusing on the histological structure and signs of inflammation and fibrosis. Patients and Methods: We evaluated consecutive patients with DO that received BoNT intradetrusor injections. We analyzed inflammation and fibrosis in 36 patients, divided into two groups based on their history of BoNT treatment. Our patients underwent at least one round of injections and specimens were compared individually, before and after each injection. Results: A decrease in inflammation was found in 26.3% of the cases, a reactive increase in 31.5%, and no change in 42.1%. No de novo or increase in preexisting fibrosis was found. In some cases, fibrosis diminished after a second round of BoNT. Conclusion: In most cases, BoNT intradetrusor injections in DO patients showed no effect on bladder wall inflammation and actually improved the inflammatory condition of the muscle in a significant number of samples.