Histological changes in the urothelium and suburothelium of human overactive bladder following intradetrusor injections of botulinum neurotoxin type A for the treatment of neurogenic or idiopathic detrusor overactivity

Abstract

Background: We examined, for the first time in a prospective study, the histological changes in the urothelium and suburothelium of patients with neurogenic (NDO) or idiopathic detrusor overactivity (IDO) after one or repeat treatments with intradetrusor BoNTA.

Methods: Flexible cystoscopic bladder biopsies were obtained from patients with urodynamically proven intractable spinal NDO or IDO before and 4 and 16 wk after one or repeat treatments with intradetrusor injections of BOTOX1 (NDO 300 U, IDO 200 U). Specimens were stained for haematoxylin-eosin and analysed blindly for inflammatory changes, fibrosis, hyperplasia, and dysplasia in the urothelium and suburothelium. Statistical comparisons were significant at p values less than 0.05.

Results: Signs of chronic inflammation were found in 59.1% of baseline biopsies (65.6% of NDO vs. 50% of IDO, p=0.049), 67.6% of post-first biopsies and 86.4% after repeat injections. The two groups were comparable for degree of baseline inflammation, which did not change significantly after first injection and up to 16 wk after a third injection. Mild fibrosis was found in 2.2% of biopsies examined, equally before and after treatment, but not after repeat injections. No dysplasia or hyperplasia was identified. Eosinophils were identified more frequently in biopsies taken after repeat injections compared with the post-first injection and baseline biopsies (chi2=8.23, p=0.018). No difference existed between NDO and IDO bladders.

Conclusions: BoNTA injections do not appear to be producing significant inflammatory changes, fibrosis, or dysplastic changes in human bladder urothelium/suburothelium after a single injection and in a limited number of repeat treatment biopsies. The presence of eosinophils might be treatment-related, because they were mostly found in post-treatment biopsies.