Relationship between anal functional lumen imaging probe (EndoFLIP®) results and the clinical presentation of faecal incontinence.

Aim: Faecal incontinence (FI) subtypes (urge, passive, mixed) are linked to the physiopathological mechanism of FI. Previous studies have failed to demonstrate a consistent relationship between FI subtype and anal sphincter dysfunction. Our aim was to evaluate the relationship between anal sphincter function, assessed using the new EndoFLIP® technology, and FI subtype.

Method: Patients referred for FI were prospectively enrolled between October 2015 and May 2021 in a registry, and data were retrospectively examined. Each patient underwent a clinical assessment as well as three-dimensional high-resolution or water-perfused anorectal manometry, anal EndoFLIP®, and anorectal electrophysiological and endoanal ultrasound tests. The results of the investigations were compared across FI subtypes.

Results: The cohort included 133 patients, 54 (41%) of whom met the criteria for urge FI, 40 (30%) for passive FI and 39 (29%) for mixed FI. The resting anal distensibility index (DI) at 50 ml of distension was significantly lower in patients with urge FI than in patients with passive FI (p = 0.04). At rest, a DI at 50 ml of distension ≥7.3 mm  mmHg and a DI at 40 ml of distension <1.3 mm  mmHg were associated with the passive and urge FI subtypes, respectively, with poor discriminatory power (an accuracy of 0.49 compared with 0.33 for random assignment). There were no differences in anorectal manometry, endoanal ultrasound or electrophysiological test results among the urge, passive and mixed FI subgroups (all p > 0.05).

Conclusion: The anal sphincter DI using the EndoFLIP® system displayed poor predictive performance in distinguishing among FI subtypes.