Original Article

Experimental Study No. 1: Directional muscle forces activate anorectal continence and defecation in the female

  • PETER PETROS
  • MICHAEL SWASH

Pelviperineology 2008;27(3):94-97

To evaluate the hypothesis that musculoelastic forces acting around the pubourethral ligament (PUL) and uterosacral ligaments (USL) play a critical role in anorectal continence and defecation in the female. X ray video recordings, including evacuating proctograms (n = 15) were made during rest, straining and squeezing in 25 patients with urinary and fecal incontinence (FI), with radio-opaque dye in bladder, vagina, rectum and levator plate. There were 4 control patients. Surface intravaginal EMG recordings were made on separate occasions. During straining, a forward directional force (pubococcygeus) appeared to anchor the perineal body and anterior rectal wall; another forward vector (puborectalis, PRM), appeared to compress the posterior anorectal wall. Posterior vectors (levator plate and m. longitudinal muscle of the anus) stretched the rectum backwards/downwards to create the anorectal angle. During defecation, the observations were consistent with relaxation of PRM, allowing the other three directional muscle forces to actively open out the anterior and posterior walls of the anal outflow tract. All muscle forces except puborectalis appear to act against suspensory ligaments (PUL or USL) in anorectal closure and also, defecation. Compared to normal patients, the vagina and rectum were in quite vertical positions in the FI group, and were not angulated to the horizontal plane on straining. Vectors contracting against suspensory ligaments were demonstrated during anorectal closure and evacuation, consistent with the hypothesis.

Keywords: Pelvic muscles; Anorectal closure; Fecal incontinence; Defecation; Connective tissue, Ligaments.