**Hsiu-Jen Wang 1, Wan-Ru Yu 2, Hueih-Ling Ong <sup>3</sup> and Hann-Chorng Kuo 1,\***


Received: 18 October 2019; Accepted: 15 November 2019; Published: 19 November 2019

**Abstract:** A botulinum toxin A (BoNT-A) intravesical injection can improve the symptoms of interstitial cystitis/bladder pain syndrome (IC/BPS). Patients with IC/BPS have different clinical characteristics, urodynamic features, and cystoscopic findings. This study assessed the treatment outcomes of a BoNT-A intravesical injection and aimed to identify the predictive factors of a satisfactory outcome. This retrospective study included IC/BPS patients treated with 100 U BoNT-A. The treatment outcomes were assessed by global response assessment (GRA) at 6 months. We classified patients according to different clinical, urodynamic, and cystoscopic characteristics and evaluated the treatment outcomes and predictive factors. A total of 238 patients were included. Among these patients, 113 (47.5%) had a satisfactory outcome (GRA ≥ 2) and 125 (52.5%) had an unsatisfactory outcome. Improvements in the IC symptom score, IC problem score, O'Leary–Sant symptom score, and visual analog scale score for pain were significantly greater in patients with a satisfactory outcome than in patients with an unsatisfactory outcome (all *p* = 0.000). The IC disease duration and maximal bladder capacity (MBC) were significantly different between patients with and without a satisfactory outcome. Multivariate analysis revealed that only the MBC was a predictor for a satisfactory outcome. Patients with a MBC of ≥760 mL and glomerulations of 0/1 (58.7%) or glomerulations of 2/3 (75.0%) frequently had a satisfactory outcome. We found that BoNT-A intravesical injection can effectively improve symptoms among patients with IC/BPS, with a remarkable reduction in bladder pain. A MBC of ≥760 mL is a predictive factor for a satisfactory treatment outcome.

**Keywords:** bladder pain; botulinum toxin A; predictor; maximal bladder capacity; hydrodistention

**Key Contribution:** Single intravesical botulinum toxin A (BoNT-A) injection improved symptoms in 47.5% of IC/BPS patients. A maximal bladder capacity of ≥760 mL during cystoscopic hydrodistention predicts a satisfactory outcome, regardless of the glomerulation grade.
