Overactive bladder syndrome (OAB) is defined by the International continence Society as urinary urgency, usually accompanied by increased daytime frequency and/or nocturia, with urinary incontinence (OAB-wet) or without (OAB-dry), in the absence of urinary tract infection or other detectable disease . (1,2) In children this symptom complex generally presents with incontinence (OAB- wet) and can be divided into monosymptomatic enuresis (MNE), non-monosymptomatic enuresis (NMNE) and day-time incontinence only. Prevalence of OAB in children is reported as 1-20%. (3)
The European Association of Urology Guidelines for the treatment of OAB in both adults and children suggest lifestyle and behavioural modification as first line treatment and pharmacotherapy as second line. For adult patients with treatment refractory OAB, third line treatment recommendations include Botulinium Toxin A intradetrusor injections and neuromodulation. Neither is currently recommended for use in paediatric OAB. The European Society for Paediatric Urology (ESPU) considers Botox an experimental treatment option for children. Publications on intradetrusor Botox in incontinent children are sparse. 

We report our initial experience with intradetrusor Botox in children with OAB.

We performed a retrospective analysis of electronic hospital records between July 2016 and December 2019. We reviewed patients with incontinence who failed conservative treatment. Neurogenic patients were excluded from this review. Only Botox naïve patients receiving their first dose of 100U of Botox were included. Study parameters include pre and post-operative uroflowmetry, post void residual bladder volume and symptom improvement as reported on first clinic review, defined as fully continent, improved or no change in incontinence episodes. All patients underwent cystoscopic injection of Botox under general anaesthesia with antibiotic cover as a day case procedure.

Fifty-one patients between the ages of 6 and 15 (median 11) were included, 20 male and 31 female. Twenty-nine had non-monosymptomatic enuresis (NMNE), 15 had monosymptomatic enuresis (MNE), and 7 had daytime incontinence only. None were OAB-dry. A median of two pharmacological agents was trialled before receiving Botox.
No adverse events were reported.

Resolution of incontinence occurred in 17 patients (33%), with a further 29 (57%) reporting fewer incontinence episodes per week. Five patients reported no improvement in incontinence after Botox. (10%)
The median PVR pre operatively was 1ml as compared to 9ml post operatively.  The PVR post Botox was more than 20% of their estimated bladder capacity (EBC) in 3 patients (5.9%). All were managed conservatively, with no patient requiring intermittent catheterization.

The use of intravesical Botox for management of treatment refractory OAB in children appears safe and provides symptomatic improvement in the majority of patients.
Our results suggest a higher dose of intradetrusor Botox may be required to achieve continence in some children. Further prospective research is needed in order to determine optimal Botox dosage in this group.

Abrams, P., Cardozo, L., Fall, M., Griffiths, D., Rosier, P., Ulmsten, U., Van Kerrebroeck, P.E., Victor, A. & Wein, A. The standardisation of terminology in lower urinary tract function: report from the standardisation sub-committee of the International Continence Society. Urology 61, 37-49 (2003).
Haylen, B.T., de Ridder, D., Freeman, R.M., Swift, S.E., Berghmans, B., Lee, J., Monga, A., Petri, E., Rizk, D.E., Sand, P.K. & Schaer, G.N. An International Urogynecological Association (IUGA)/International Continence Society (ICS) joint report on the terminology for female pelvic floor dysfunction. Neurourology and Urodynamics 29, 4-20 (2010).
Bower, W.F., et al. The epidemiology of childhood enuresis in Australia. Br J Urol, 1996. 78: 602.