Authors: P Petros M Swash M Bush M Fernandez A Gunnemann M Zimmer
Publish Date: 2012/08/14
Volume: 16, Issue: 6, Pages: 437-443
Abstract
Three groups of female patients were evaluated with video imaging studies of defecation using a grid or bony reference points Eight patients with idiopathic fecal incontinence had video myogram defecography eight with obstructive defecation had magnetic resonance imaging MRI defecating proctograms and four normal patients had video Xray or MRI defecating proctogram studiesIn all three groups the anorectum was stretched bidirectionally by three directional muscle force vectors acting on the walls of the rectum effectively doubling the diameter of the rectum during defecation The anterior rectal wall was pulled forwards and the posterior wall backwards and downwards opening the anorectal angle associated with angulation of the anterior tip of the levator plate LP These observations are consistent with a staged relaxation of some parts of the pelvic floor during defecation and contraction of others First the puborectalis muscle relaxes Puborectalis muscle relaxation frees the posterior rectal wall so that it can be stretched and opened by contraction of the LP and conjoint longitudinal muscle of the anus Second contraction of the pubococcygeus muscle pulls forward the anterior rectal wall further increasing the diameter of the rectum Third when the bolus has entered the rectum the external anal sphincter relaxes and the rectum contracts to expel the fecal bolusOur results are consistent with the hypothesis that pelvic striated muscle actively opens the rectal lumen thereby reducing internal anorectal resistance to expulsion of feces Controlled studies of electromyographic activity would be useful to further test this hypothesis
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