A novel method for measurement of the recto-anal inhibitory reflex using anal acoustic reflectometry

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.

Current and future perspectives on the utility of provocative tests of anal sphincter function: A state-of-the-art summary

BACKGROUND

The maintenance of fecal continence depends upon coordinated interactions between the pelvic floor, anorectum, and anal sphincter complex orchestrated by central and peripheral neural activities. The current techniques to objectively measure anorectal function rely on fixed diameter catheters placed inside the anal canal with a rectal balloon to obtain measurements of anal resting and squeeze function, and rectal compliance. Until recently it had not been possible to measure the distensibility of the anal canal, or in other words its ability to resist opening against an increasing pressure, which has been proposed as the main determinant of a biological sphincter's function. Anal acoustic reflectometry (AAR) and the functional lumen imaging probe (FLIP) are two novel, provocative techniques that dynamically assess the anal sphincter complex under volume-controlled distension. In doing so, both provide information on the viscoelastic properties of the anal canal and offer new insights into its function.

PURPOSE

This review details the current and potential future applications of AAR and FLIP and highlights the unanswered questions relevant to these new technologies.