Evaluation of the Length of Anal High-Pressure Zone as a Barrier for Fecal Incontinence

Fecal incontinence (FI) is a multifactorial problem. The length of the anal high-pressure zone (HPZ) may serve as an independent barrier for anal continence, but its role in the pathogenesis of FI has not been examined. We evaluated the association between the length of anal HPZ and anal sphincter pressures in FI patients with or without anal sphincter defects and compared this with healthy controls.

Patients with FI (≥2 episodes per month) underwent high-resolution anorectal manometry and anal ultrasound tests to assess the anal HPZ, anal sphincter pressures and anal morphology. Data were compared between FI patients with and without sphincter defects and healthy controls.

We evaluated 224 FI patients and 34 controls. About 33.0% (74/224) of FI patients had anal sphincter defects. The length of anal HPZ was not different between patients with or without sphincter defects (P=0.571). The HPZ was shorter in FI patients than in controls (P<0.001). It was weakly associated with age, number of leakage episodes, and anal resting pressure in FI patients without (r<0.301, P<0.011) but not with sphincter defects (r<0.142, P>0.092). The lengths of HPZ during voluntary squeeze and reflex anal squeeze pressures were not correlated in both groups (r<0.156, P>0.184), except for a weak association in patients with defects (r=0.163, P=0.048).

The length of anal HPZ is shorter in FI patients but is not associated with the strength or intactness of anal sphincter muscles, and FI episodes. The length of anal HPZ may not affect anal barrier function.