Evaluation of pre-operative bladder contractility as a predictor of improved response rate to a staged trial of sacral neuromodulation in patients with detrusor underactivity.

Purpose: Sacral neuromodulation (SNM) is one of the few management options shown to improve outcomes in patients with detrusor underactivity (DU). This original research will investigate if preserved bladder contractility can predict a successful treatment with SNM.

Methods: This is a retrospective study of a prospectively collected database of consecutive patients with DU, who had a staged SNM trial from January 2013 to December 2018, with a minimum of 12 months follow-up. The primary outcome was the success of stage 1 SNM trial.

Results: In total, 69 patients with DU were followed. The median age was 67 [interquartile range (IQR) 74-55], median baseline bladder contractility index (BCI) 18 (IQR 67-0), and median post-void residual 200 mL (IQR 300-130). There were 35 patients (51%) that responded to a SNM trial. At a median follow-up of 23 months (IQR 39-12), three were removed for poor efficacy. In patients with detrusor acontractility (DAC), six responded (33%), compared to 29 patients (57%) with BCI > 0. This was statistically significant, p value 0.03. Younger age was also a predictive factor for SNM response, p value 0.02. There were no differences noted in those with gender, neurogenic history, previous pelvic surgery, diabetes, or pre-operative voiding history.

Conclusion: Our study showed that patients with preserved bladder contractility are more likely to respond to a trial of SNM compared with those that have DAC. Younger age was also predictive of SNM response. UDS is the only method to accurately identify DAC patients. This information will help in patient selection and pre-operative counselling.