Intradetrusor onabotulinumtoxinA (BoNT-A) injections are a well-established therapy for refractory neurogenic and non-neurogenic detrusor overactivity (DO). While urodynamic investigation (UDI) might be necessary after treatment in patients with maximal storage detrusor pressure (Pdetmax) > 40 cm H2O cm to monitor the effect of the injections on bladder pressure in neurogenic DO (1), its value in the non-neurological population remains unclear. Our aim was to evaluate whether patients’ treatment satisfaction after intradetrusor BoNT-A injections for non-neurogenic DO is sufficient for adequate outcome evaluation, or if UDI is necessary.

In our combined retrospective and prospective study, we analyzed 40 patients (20 females, 20 males) undergoing intradetrusor BoNT-A injections for refractory non-neurogenic DO in two university hospitals from January 2018 to June 2023. 52.5% of the patients received 100 units, 5% 150 units, and 42.5% 200 units of BoNT-A. Patients underwent UDI both before and 6-12 weeks after intradetrusor BoNT-A injections. The primary outcome measure was the prevalence of Pdetmax >40 cmH2O in patients which were satisfied with the treatment. Satisfaction was assessed by questionnaires, medical history, and achievement of urinary continence. Secondary outcome measures were treatment effects on various clinical and urodynamic variables.

After intradetrusor BoNT-A injections, 22 of 40 patients (55%) were satisfied. Of these, 4 patients (18%) had a Pdetmax >40 cmH2O (Table 1). The maximal cytometric capacity (MCC) measured 6-12 weeks after BoNT-A injections was significantly higher in the satisfied compared to the unsatisfied group (Table 2). Only 7 of the 40 patients (17.5%) had no DO after BoNT-A injections.

McGuire et al. correlated Pdetmax >40 cmH2O to a higher risk of vesicoureteral reflux, establishing this cutoff as a prognostic marker for upper urinary tract injury (2). While no subsequent scientific investigations have further explored this marker, it has been widely adopted as a prognostic threshold in clinical practice. Patients with non-neurogenic DO are considered to have a lower risk of upper urinary tract impairment; thus, treatment outcome of BoNT-A injections is evaluated mainly by clinical response (e.g. achievement of continence). In our cohort, a notable subgroup with baseline Pdetmax >40 cmH2O would benefit from UDI after BoNT-A injections, since 18% (4/22) of satisfied patients with treatment outcome still had a Pdetmax >40 cmH2O.

In patients with refractory non-neurogenic DO and urodynamic baseline Pdetmax >40 cmH2O, treatment satisfaction alone is inadequate for outcome assessment after intradetrusor BoNT-A injections, as high storage detrusor pressures (>40 cmH2O) jeopardizing the upper urinary tract might be missed in almost one out of five satisfied patients. Therefore, we recommend UDI (i) before the first BoNT-A injections treatment (baseline) and (ii) after the injections in the subgroup of patients with baseline Pdetmax >40 cmH2O.

Koschorke, M., Leitner, L., Sadri, H., Knüpfer, S.C., Mehnert, U. and Kessler, T.M. (2017), Intradetrusor onabotulinumtoxinA injections for refractory neurogenic detrusor overactivity incontinence: do we need urodynamic investigation for outcome assessment?. BJU Int, 120: 848-854. https://doi.org/10.1111/bju.13976
McGuire, E. J., Woodside, J. R., Borden, T. A., & Weiss, R. M. (1981). Prognostic value of urodynamic testing in myelodysplastic patients. The Journal of urology, 126(2), 205–209. https://doi.org/10.1016/s0022-5347(17)54449-3