Provocative Tests of Anal Sphincter Function Correlate with Symptoms and Subtypes of Faecal Incontinence

Objectives
High-resolution anorectal manometry (HRAM) is the established investigation in faecal incontinence (FI). However, provocative tests (functional lumen imaging probe (FLIP) and anal acoustic reflectometry (AAR)) have been proposed as alternatives. This study uniquely explores all three methods in correlation with FI symptoms and subtypes.

Methods
This was a prospective observational study of FI patients attending a tertiary pelvic floor unit between August 2022 - January 2024. Patients underwent HRAM, FLIP and AAR with the order randomised. FI severity was assessed with the Vaizey score and quality-of-life with the Manchester Health Questionnaire.

Results
Forty patients (39 female, median age: 62 [range: 38–85]) were recruited with 27 (67.5%) reporting urge FI, eight (20%) mixed, and five (12.5%) passive incontinence.
FLIP squeeze measurements correlated with the Vaizey score, including incremental squeeze pressure at 40ml (rs=-0.412; p=0.008) and 50ml (rs=-0.414; p=0.009) and the pressure-diameter volume loop at 50ml (rs=-0.402; p=0.011). Incremental squeeze opening pressure with AAR correlated with the Vaizey score (rs=-0.339; p=0.032). There was no correlation between symptom severity and HRAM parameters, or any parameter and quality-of-life scores.

Resting parameters with all three modalities were lower in passive FI: mean resting pressure (HRAM; p=0.010), yield pressure (FLIP; p=0.031) and opening pressure (AAR; p=0.006). With FLIP, there was a trend towards reduced squeeze function in the urge group (pressure-diameter volume loop at 50ml; p=0.295).

Conclusions
FLIP and AAR correlate better with FI symptoms compared to HRAM. Therefore, these provocative tests could be used to guide the management of FI in prospective studies.