Importance of extrasphincteric mechanisms in the pathophysiology of faecal incontinence in adults with a history of anorectal anomaly

Abstract

Although surgery for congenital anorectal anomalies (ARAs) aims to preserve anorectal function, faecal incontinence and constipation often result. Apart from the anal sphincters, continence is dependent on multiple anatomical and physiological factors. The aim of this study was to evaluate adults with a history of ARA to determine the role of such factors in functional outcome. The study included 20 consecutive adult patients with faecal incontinence who had undergone anorectal surgery as infants. Comprehensive testing included anal manometry, endoanal ultrasonography, tests of pudendal nerve function and rectal sensory function, evacuation proctography and colonic transit studies. Anal resting tone and squeeze increments were both attenuated in 15 of 19 patients. Integrity of the internal and external anal sphincters was compromised in 16 and 15 of 18 patients respectively. Eleven of 13 had evidence of pudendal neuropathy. Rectal sensation was abnormal in 14 of 18 patients, of whom ten were hypersensitive and four hyposensitive. Rectal evacuation was abnormal in nine of 14. Colonic transit was delayed in five of eight patients with constipation. Faecal incontinence in adult patients with ARA is related to various pathophysiologies. Structural integrity of the anal sphincters is a major factor, but extrasphincteric mechanisms, notably rectal sensory function, may be as important.