State of the art: pathophysiologyPathophysiology of adult fecal incontinence
Section snippets
Structure and function of the anorectum
The rectum is a hollow muscular tube, 12 to 15 cm long, composed of a continuous layer of longitudinal muscle that interlaces with the underlying circular muscle.2 The anus is a muscular tube 2 to 4 cm long. At rest, it forms an angle of approximately 90 degrees with the axis of the rectum. During voluntary squeeze the angle becomes more acute, whereas during defecation, the angle becomes more obtuse (Figure 1).
Anorectal sensation
An intact sensation not only provides a warning of imminent defecation, but also helps to discriminate between formed stool, liquid feces, or flatus. Elderly persons,100 physically and mentally challenged individuals, and children with fecal incontinence101 often show blunted rectal sensation. Impaired rectal sensation may lead to excessive accumulation of stool, causing fecal impaction, mega-rectum (extreme dilation of the rectum), and fecal overflow.100, 101 Causes of impaired sensation
Miscellaneous
A variety of medical conditions and disabilities may predispose to fecal incontinence, particularly in the elderly. Immobility and lack of access to toileting facilities are primary causes of fecal incontinence in this population.107 Several medications may inhibit sphincter tone—for example, anticholinergics, some of which are used to treat urinary incontinence and detrusor muscle instability, include tolterodine tartarate (Detrol), Pharmacia, Kalamazoo, MI; oxybutynin (Ditropan), Alza
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