Coexistent overactive-underactive bladder (COUB) syndrome: A multicentre Italian study

Introduction and aim of the study: Low evidence is available on the efficacy of sphincterotomy and intra-sphincteric botulinum toxin injection in the treatment of detrusor-sphincteric dyssynergia (DSD) in spinal cord inured (SCI) patients. The aim of the present study is to compare the outcomes of sphincterotomy and sphincteric botulinum toxin A (Botox) injection in the treatment of DSD in SCI patients. Materials and methods: It is a retrospective observational study conducted on consecutive patients affected by neurogenic bladder after SCI subjected to sphincterotomy or intra-sphincteric Botox injection for the treatment of DSD between 2001 and 2019 in a tertiary referral Centre. Included patients underwent previous and subsequent radio-urodynamic studies, demonstrating DSD associated to voiding dysfunction. Residual vesical volume after reflex micturition and maximum detrusor pressure were assessed before and after the surgical procedure. Patients were considered suitable for exclusive reflexed bladder emptying whenever residual volume was <150 ml (clinical success). Chi-squared tests and Mann–Whitney’s U tests were used for subgroup analysis. Results: 18 patients subjected to intra-sphincteric Botox injection and 15 subjected to endoscopic sphincterotomy were included. Median age at surgery was 54 (IQR47-63). Median follow up was and was 180 months in the sphincterotomy group and 40 months in the Botox group, p=0.001. No statistically-significant differences were found between groups in baseline characteristics. Clinical success was achieved in 15 patients subjected to Botox (79%) and 13 subjected to sphincterotomy (93%), p=0.35. Any significant difference was found between median decrease of residual bladder volume after voiding (130 ml vs 150 ml respectively, p=0.72) and of median decrease in voiding detrusor pressure (12.5 cmH20 vs 20 cmH20 respectively, p=0.60). 2 early complications were observed in the Botox group (urinary tract infection) and in 1 in the sphincterotomy group (persistent hematuria). Median duration of clinical effectiveness was 12 months in the Botox injection group and 80 months in the sphincterotomy group (p<0.001). Interpretation of results: Any statistically significant difference between the main outcomes between the two techniques was found. Complication rate was low in both groups, despite sphincterotomy is a more invasive procedure and requires more operative time and postoperative bladder irrigation. The duration of efficacy of the Botox procedure is lower than sphincterotomy and patients usually requires periodic reintervention. According to our study, the duration of Botox injection is higher than usually reported. Conclusions: Both sphincterotomy and intra-sphincteric botulinum toxin injection are reliable techniques to address DSD in SCI patients. Given the limited duration of intra-sphincteric botulinum toxin injection, it could be proposed as a test of efficacy before sphincterotomy.