To investigate the role of onabotulinum toxin A (BTX-A) injections in patients with failed augmentation cystoplasty for neuropathic or idiopathic detrusor overactivity (NDO or IDO).

A retrospective review of all cystoplasty patients who underwent BTX-A injection at a tertiary centre between 2008-2019. Details including indications and time from cystoplasty, video-urodynamic, BTX-A dose and clinical outcomes were analysed. Telephone interview were performed for patients that requested repeat BTX-A injections. The interview included PGIC7 and UDI6 questionnaires. A positive clinical response was considered improvement of overactive symptoms sufficient to merit repeat BTX injection and a PGIC7 of 4 or above.

30 patients were identified (11 men and 19 women). The indications for augmentation were IDO (n=18) or NDO (n=12). Mean age at the time of cystoplasty was 42 years (range 10-61)
Interval between cystoplasty and initial BTX-A was 98 months (range 3-271). Video-urodynamics before BTX-A revealed loss of compliance (LOC) in 13 patients, DO in 22 patients, and combined LOC/DO in 10. The median bladder capacity was 338mls (range 77-570ml). 
13 patients responded to BTX-A injections. Higher peak DO pressure was associated with a significantly higher chance that the patient would experience benefit from the injections (p=0.026).
The patients that responded to BTX-A underwent a total of 115 procedures (mean 8.8 injections) over a mean 88 months (range 20-157 months).

The only predictor of response in our series was peak detrusor pressure. This may reflect residual overactivity primarily in the bladder segment, as overactivity related to bowel peristalsis would be expected to be more consistent pressure, and compliance loss a steady state pressure related to volume. More work is required to assess whether this hypothesis can guide therapy and predict outcome.

This study is a reflection of our clinical experience with an uncommon and challenging patient cohort. As such, the study has limitations. The retrospective analyses did not allow assessment by the commonly used criteria for BTX-A studies, and indeed frequency-volume and incontinence charts would be difficult to achieve in many of these complex patients. We tried to compensate for this using phone administration of questionnaires. In future theses questionnaires will be used in a prospective fashion. The study is also limited by the heterogeneous population and small sample size, inherent to the rarity of the circumstances

Forty-three percent of patients responded well to intra-detrusor BTX-A injections. This avoided the need for more invasive surgery and had a positive impact on their quality of life.

Overactive Bladder (OAB) Guideline - American Urological Association [Internet]. [cited 2020 Mar 21]. Available from: https://www.auanet.org/guidelines/overactive-bladder-(oab)-guideline
Biers SM, Venn SN, Greenwell TJ. The past, present and future of augmentation cystoplasty [Internet]. Vol. 109, BJU International. 2012 [cited 2020 Mar 21]. p. 1280–93. Available from: http://www.ncbi.nlm.nih.gov/pubmed/22117733
Mehmood S, Alhazmi H, Al-Shayie M, Althobity A, Alshammari A, Altaweel WM, et al. Long-term outcomes of augmentation cystoplasty in a pediatric population with refractory bladder dysfunction: A 12-year follow-up experience at single center. Int Neurourol J. 2018 Dec 1;22(4):287–94