Baseline Anal Sphincter Elastance May Predict Long-Term Outcomes of Sacral Neuromodulation for Fecal Incontinence

Introduction: Anal acoustic reflectometry (AAR), a novel test of anal sphincter function, was shown to predict a successful trial phase of sacral neuromodulation (SNM) for fecal incontinence. This follow-up study aims to explore if AAR can also predict short- and long-term SNM outcomes at less than and more than 5 y, respectively.

Methods: Outcome data were reviewed from a prospectively managed database. Successful treatment was defined as >50% improvement in patient reported fecal incontinence or urgency episodes, or in a symptom severity score.

Results: Twenty-six female patients (median: 53 y [range 31-80]) who received a permanent SNM implant were analyzed. In the short-term, no differences were observed in baseline AAR and symptom severity parameters between patients reporting success or failure. At long-term follow-up (median: 122 mo [113-138]) data was available from 17 (17/26, 65%) patients with 7 (7/17, 41%) reporting continued treatment success. Baseline fecal urgency episodes (P = 0.003), and the AAR parameters of opening elastance (P = 0.043) and squeeze opening elastance (P = 0.025) were significantly different between patients reporting success and those reporting failure. Squeeze opening elastance demonstrated the greatest ability to discriminate between success and failure (area under the curve: 0.82 (95% confidence interval 0.60-1.01, P = 0.003)).

Conclusions: AAR may have a role in identifying patients suitable for SNM treatment with clinically relevant metrics associated with successful response to treatment. Future work should explore this further to improve SNM patient selection.