The relationships between the results of contemporary tests of anorectal structure and sensorimotor function and the severity of fecal incontinence.

Abstract

Diagnostic investigations for fecal incontinence (FI) assess the structure and sensorimotor function of the anorectum. Investigations include anorectal manometry, anorectal sensory testing, pudendal nerve terminal motor latencies (PNTML), and endoanal sonography. The severity of FI and results of investigations are often discordant andtherate of symptom resolution following treatment remains <40%. High-resolution anorectal manometry (HRAM) and three-dimensional endoanal ultrasound (3D-US) have been introduced during the last decade.This study aims to assess the strength of relationships between contemporary investigation results and FI severity. Adults presenting for investigation of FI were assessed using the St Mark's FI severity score (SMIS),HRAM, anorectal sensory testing, PNTML, and 3D-US. 246 patients were included.There were significant relationships between the SMIS andHRAM (resting pressure rs = -0.23, 95% CI = (-0.34, -0.11), P<.001; squeeze pressure (rs = -0.26, 95% CI = (-0.37, -0.14), P< .001) and 3D-US (anterior EAS length rs = -0.22, 95% CI = (-0.34, -0.09), P= .001). The relationships between SMIS and HRAM had a greater effect size in those with urge-predominant symptoms (resting pressure: rs = -0.40, 95% CI = (-0.57, -0.20), P< .001, squeeze pressure: rs = -0.34, 95% CI = (-0.52, -0.12), P= .003).Overall, the variance in SMIS accounted for by anorectal investigations was 8.6% (R2 = 0.098, adjusted R2 = 0.086, P < .001). Anorectal investigations are not strong predictors of FI severity. These findings may reflect the multifactorial, heterogeneous pathophysiology of FI, the limitations of the SMIS and anorectal investigations, and contributing factors extrinsic to the anorectum.