Lettsomian lectures. A neurologist's view of coloproctology and the pelvic floor and incontinence: new light on an old problem.

In idiopathic anorectal incontinence there is weakness of the pelvic floor sphincter muscles. This is evident on digital examination of the external anal sphincter muscle, and can be confirmed by anorectal manometry. This pelvic floor weakness is commonly associated with abnormal descent of the pelvic floor below the plane of the perineum during straining, as during the act of defaecation. This perineal descent is itself a feature of weakness of these muscles as shown by the prominent appearance of this sign in patients with cauda equina lesions. Almost all patients with this syndrome are women and there is usually a history of prolonged or difficult childbirth, often followed by a change in bowel habit, with prolonged and persistent straining at stool. However, not all affected women have experienced childbirth. In the latter a similar pattern of abnormal defaecation is present, but the reason for this is unknown. Anorectal incontinence is associated with urinary incontinence of the stress type in 10-15% of patients.