Onabotulinum Toxin A Intradetrusor Injections in Children with Neurogenic Lower Urinary Tract Dysfunction: Long-Term Histological Effects on the Bladder Wall

BACKGROUND

In the last twenty-five years, Onabotulinum Toxin A (BTX-A) has gained increasing popularity for neurogenic lower urinary tract dysfunction (NLUTD) treatment. To maintain its efficacy, repeated BTX-A intradetrusor injections are required over time, with unknown effects on the bladder wall in children. The aim of this paper is to report long-term effects on the bladder wall in children treated with BTX-A.

METHODS

Children with NLUTD not responsive to anticholinergics were treated with BTX-A, according to our protocol, with bladder wall control using endoscopic cold-cup biopsy. Specimens were evaluated considering edema, chronic inflammation, and fibrosis.

RESULTS

Of the 230 patients treated from 1997 to 2022, we considered only specimens obtained in patients who had received ≥5 treatments (36 children), considered as the threshold to evaluate clinical effectiveness on long-term treatment with BTX-A. Most of them had congenital NLUTD (25 patients) and detrusor overactivity (27 patients). In all, increased edema and chronic inflammation with reduced fibrosis over time was reported; these data were not statistically significant. No difference was observed between patients with congenital and acquired diseases.

CONCLUSIONS

Repeated intradetrusor BTX-A injections are not related to significant histological alterations in children, similarly with adults, and repeated injections could be considered safe.

Urothelium removal does not impact mucosal activity in response to muscarinic or adrenergic receptor stimulation

The inner lining of the urinary bladder (urothelium and lamina propria, or bladder mucosa) has an important role as a tissue barrier between stored urine and the underlying smooth muscle, as well as in the modulation and regulation of bladder contractility. However, the individual influence of the apical urothelial layer on the contractile activity of this tissue is uncertain. The aim of this experiment was to identify the contractile activity of the lamina propria after removal of the urothelium. Several methods were used to mechanically disrupt the urothelium, including dabbing the tissue with a paper towel, longitudinal swipes with a cotton bud, or a longitudinal scrape with the edge of a scalpel. Hematoxylin-eosin staining was utilized to determine the level of removal of the apical urothelial cells. Spontaneous contractile activity was measured in organ baths, and responses to the agonists carbachol and isoprenaline were obtained. Three longitudinal swipes with a cotton bud was found to be the optimal method to remove the majority of the urothelium without damaging the lamina propria. Upon removal of the urothelium, the spontaneous activity of the tissue was unaltered. Similarly, responses to carbachol (1 µM) and isoprenaline (1 µM) were not affected after removal of the urothelium. The urothelium can be effectively removed without damaging the lamina propria. This apical tissue layer is not responsible for mediating the increases to spontaneous phasic activity or tonic contractions of the bladder mucosa (urothelium with lamina propria) when muscarinic or adrenergic receptors are stimulated. This research presents the lamina propria as the important cell layer mediating the overall contractile activity of the bladder wall.