Systematic Evaluation of External Anal Sphincter Fatigability in Healthy Women and Women With Fecal Incontinence: A High-Resolution Anorectal Manometric Study

Background/Aims: International consensus guidelines recommend assessing the external anal sphincter (EAS) function using a short maximal contraction.The clinical value of sustained contractions for assessing EAS fatigability remains controversial, partly because most studies have used water-perfused anorectal manometry systems rather than the more recent three-dimensional high-resolution anorectal manometry (3D HR-ARM) approach.We aimed to determine the discriminative ability of EAS fatigability between patients with fecal incontinence (FI) and healthy volunteers (HV), as well as its pathophysiological implications in patients with FI assessed using 3D HR-ARM.Methods: 3D HR-ARM data from 160 adult female with FI (median age, 64 years) were compared with data from 39 healthy female volunteers (median age, 52 years; P < 1.10 -3 ).EAS fatigability was assessed during a long squeeze (LS) using mean incremental LS pressure (LSP), LS duration, fatigue rate index, and contractile integral (CI).Patients additionally underwent endoanal ultrasound and anal sphincter electromyography.The discriminative performance was evaluated through repeated cross-validation using logistic regression and classification and regression tree models.Results: The most discriminative model for distinguishing FI from HV combined resting pressure (RP) with maximal incremental LSP (area under the ROC curve [AUROC], 0.82; sensitivity, 0.91; specificity, 0.72).RP combined with LS duration showed similar discrimination, but lower specificity (AUROC, 0.82; sensitivity, 0.94; specificity, 0.44).Maximal incremental short squeeze pressure and maximal incremental LSP were associated with neuropathic processes (P = 0.031 and P = 0.034, respectively).Conclusions: EAS fatigability during LS, assessed using 3D HR-ARM, did not discriminate between patients with FI and HV, nor did it identify specific pathophysiological mechanisms.