Sacral neuromodulation (SNM) is used as a third line treatment option for refractory overactive bladder (OAB). We previously reported our findings that patients who experience a greater than 75% improvement in their symptoms during SNM testing (SNM I) appeared to have greater long term efficacy compared to those with a 50-75% improvement [1]. As well, we noted a possible positive association between the presence of stress urinary incontinence (SUI) and the outcome of SNM. Herein we examine more closely the issue of SUI and SNM outcomes.

Our prior study was a retrospective review of 137 patients undergoing SNM for OAB who had an at least 50% improvement in symptoms during SNM I testing (either peripheral nerve evaluation, PNE test, or staged implant testing). For the current study, we reviewed these patients as well as patients who experienced <50% improvement in symptoms and identified all patients who had also reported having subjective SUI (sSUI): they answered yes to a question regarding the presence of incontinence with activity/straining/coughing.  Patients not reporting sSUI were exlcuded. Patients were grouped based on the degree of symptomatic improvement during SNM I testing: 50-75% (group 1), >75% (group 2) and <50% (group 3) as determined by a combination of overall subjective impression of improvement, bladder diary and pad usage. We then determined if there were any differences between the groups with respect to the presence of objective SUI (oSUI). oSUI was defined via positive cough stress test (CST) in the clinic or during UDS leak point pressure (LPP) testing. Clinic CST was done in the lithotomy position, having the patient cough forcefully multiple times, although bladder volume at the time of CST was not specified. UDS was performed in concordance with ICS guidelines at medium fill rate (30mL/min) in the seated or standing position. LPP testing was performed at infused volumes of 150mL and then at capacity, with both valsalva and cough. The presence of visible SUI was noted and the lowest LPP recorded. Patient demographic, clinical and UDS variables were compared between the cohorts using chi-squared and t-test analyses.

A total of 99 female patients were included in this study. They were fairly evenly distributed as far as subjective improvement after SNM I and there were no significant differences between clinical and urodynamic parameters between groups (table 1). Despite the presence of sSUI, only 16/99 (16%) of patients were found to have oSUI on clinic CST and/or UDS LPP testing. There was no difference in the presence of oSUI between the 3 groups.

Our prior study noted an association between the presence of sSUI and SNM success. However, on closer analysis, the overwhelming majority of our patients with sSUI did not have oSUI calling into question whether or not these patients truly have SUI despite subjectively believing they do.  It is possible that these patients are experiencing stress induced detrusor overactivity (DO) rather than genuine SUI. This could explain why these patients do well with SNM.

The presence of SUI in patients with OAB does not appear to be associated with the outcome of SNM.

Charles, DK, Everett, RG, Prebay, ZJ, Landowski, TP, O'Connor, RC, Guralnick, ML. Is a 50% improvement threshold adequate to justify progression from sacral neuromodulation testing to implant? Neurourology and Urodynamics. 2021; 40: 1524- 1531.