Artificial Urinary Sphincter (AUS) is currently the best choice for post-radical prostatectomy urinary incontinence (PRPUI) [1,2]. However, substantial number of patients complain of lower urinary tract symptoms including overactive bladder (OAB) after AUS implantation requiring medical treatment [3]. Furthermore, some are refractory to drug therapy. Medication refractory post-AUS OAB is a troublesome problem adversely affecting the patient satisfaction after AUS implantation. However, there is little information available to predict which patients have the potential to suffer from medication refractory post-AUS OAB. We investigated the prevalence and differential patient characteristics of medication refractory OAB observed after AUS implantation for PRPUI.

With approval of Institutional Review Board, cases of AUS for PRPUI by a single surgeon, performed from February 2008 to January 2018, with follow up more than 6 months after device activation were evaluated retrospectively. All the patients had received radical prostatectomy for prostate cancer, and every patient underwent urodynamic study in compliance with International Continence Society standards, prior to AUS implantation. OAB was defined based on the OAB symptom score (OABSS); regarding as OAB when total score is more than 3 points with urgency score more than 2 points. Medication refractory OAB was defined when the OABSS, checked during medication (anticholinergics or β3-adrenoceptor agonist or combination of both), corresponds to the criteria of OAB. Patient general characteristics, preoperative urodynamic parameters, and medication regimen were compared grouped by response to medical treatment. Additional comparison was performed regarding the beginning of symptom onset, before or after post-AUS 1 year; an approximate time point to estimate the influence of surgery [3] . Statistical analysis was performed with Mann-Whitney U test for continuous variables, and with Chi-squared test or Fisher’s exact test for categorical variables (SPSS version 23, Chicago, IL, USA).

A total of 132 patients of AUS with PRPUI were reviewed. During the mean follow up period of 43.2 months, 57 (43.2%) patients experienced OAB requiring medical treatment with anticholinergics or β3-adrenoceptor agonist or combination of both. For 39 (29.5%) patients medication-requiring OAB symptoms appeared within 1 year after surgery (early-onset OAB), and for 18 (13.6%) patients medication requiring OAB developed after postoperative 1 year (late-onset OAB). The number of patients with preoperative maximum cystometric capacity (MCC) less than 300ml (P=0.041) or with preoperative involuntary detrusor contraction (IDC) (P=0.010) was significantly higher in early-onset OAB group (Table 1). The response to medication was evaluated in patients taking drug for more than 3 months. The total duration of medication was significantly longer in medication refractory group in both early (P=0.028) and late-onset OAB group (P=0.041). Preoperative presence of IDC was significantly associated with unresponsiveness to medical treatment in early-onset OAB group (P=0.005). In late-onset OAB group, the drug regimen was significantly different based on the treatment responsiveness, showing predominance of combination therapy (with anticholinergics and β3-adrenoceptor agonist) in medication refractory group (P=0.005) (Table 2).

In comparison of patient characteristics based on symptom onset period, there are some points to pay attention although not statistically significant. The history of cerebrovascular accident and the history of spine surgery or spinal cord disease were dominant in the early-onset OAB group. Pelvic radiation was also dominant in early-onset OAB group. The proportion of patients with preoperative bladder compliance less than 20 ml/CmH2O was dominant in early-onset OAB group. More patients with history of cerebrovascular accident were refractory to medical treatment in early-onset OAB group. Regarding the responsiveness to medication, the duration of medication was significantly longer in medication refractory group suggesting that the lack of response to drug is due to the patient intrinsic factors rather than to insufficient medical therapy. The combination treatment of anticholinergics and β3-adrenoceptor agonist was significantly predominant in medication-refractory, late-onset OAB group. This result seems to be caused by patient poor response to any drug, rather than poor efficacy of the combination therapy.

After AUS for PRPUI, more than 40% of patient experience OAB requiring medication. Patients with preoperative IDC or small MCC are more likely to present with medication-requiring OAB within one year after AUS. Patients with preoperative IDC also have potential to be refractory to medical treatment. Development of third-line therapy targeted on IDC might be useful in management of medication refractory post-AUS OAB.

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Lai HH, Boone TB. Implantation of artificial urinary sphincter in patients with post-prostatectomy incontinence, and preoperative overactive bladder and mixed symptoms. J Urol 2011;185:2254-9.