Handa 9781496386441 Full Sample Chap 1

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CHAPTER 1  Surgical Anatomy of the Female Pelvis

enterocele, perineal bulge, or a combination of these findings. Clinical findings are partly explained by defect location and changes in associated muscle, connective tissue, and nerves. Various levels of vaginal support pre- viously described provide a template for understanding the functional network involved in pelvic floor support of the posterior compartment. The upper third of the posterior vaginal wall is supported by the uterosacral ligaments and is bounded posteriorly by the cul-de-sac, described later. The rectovaginal space begins distal to the cul-de-sac peritoneum and extends inferiorly to the perineal body. Histologic analysis of this compartment shows a loose fibroadipose layer with slightly inter- spersed bands of fibrous tissue between the vagina and rectum. Descriptions of tissue composition between the vagina and rectum are variable, but indicate a growing consensus that there is no true “rectovaginal fascia” or Denonvilliers fascia. Despite these histologic findings, the Terminologia Anatomica still includes the term “rec- tovaginal fascia.” The rectovaginal space can generally be effortlessly developed below the posterior peritoneal reflection for 4 to 5 cm to the level of the perineal body apex. Although no discrete separate fascial layer has been noted, lateral projections of vaginal adventitia to the endopelvic fascia, pelvic sidewall connective tissue, and levator ani muscles have been consistently observed. Therefore, the tissue plicated at the time of posterior colporrhaphy is likely derived from a splitting of the posterior vaginal wall (encompassing the muscularis and adventitia) and/or the anterior rectal wall. Gross examination can be misleading as manipulation of the tissue can artificially create a tissue layer that can be misconstrued as a separate fascial layer. The distal third of the posterior vaginal wall is sepa- rated from the anal wall by the perineal body, which includes the anal sphincter muscles. The perineal body histologically encompasses a central fibrous connection

between the two halves of the perineal membrane, and it extends cranially for 2 to 3 cm above the hymenal ring. In this section, there is no plane of separation between the vaginal wall and anus histologically. Identifying loss of support at one or more vaginal segments (distal, mid, proximal) can help direct methods of surgical repair including perineorrhaphy, posterior colporrhaphy, or sacral colpoperineopexy. Urethral Support The support of the proximal urethra plays a role in the maintenance of urinary continence during times of increased abdominal pressure. Although it is now known that stress incontinence is primarily caused by a weak urethral sphincter mechanism (low urethral clo- sure pressure), urethral support does play an important, if secondary, role. The distal portion of the urethra is inseparable from the vagina because of their common embryologic derivation from the urogenital sinus. These tissues are fixed firmly in position by connections of the periure- thral tissues and vagina to the pubic bones through the perineal membrane. Cranial to this, beginning in the midurethra, a hammock-like layer composed of the endopelvic fascia and anterior vaginal wall provides the support of the proximal urethra ( FIG. 1.30 ). This layer is stabilized by its lateral attachments to both the ten- dinous arch of pelvic fascia and the medial margin of the levator ani muscles. The muscular attachment of the endopelvic fascia allows contraction and relaxation of the levator ani muscles to elevate the urethra and to let it descend. It had previously been thought that the status of the urethral support system was the primary factor deter- mining whether a woman had stress incontinence of urine. Recent studies have, however, shown that the strength of the urethral sphincter mechanism is the

I

Arcus tendineus fascia pelvis

Urachus

Ureter

Endopelvic fascia/ paracolpium

Bladder

Anterior vaginal wall

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Rectum

FIGURE 1.30  Lateral view of the urethral supportive mechanism transected just lateral to the midline. The lat- eral wall of the vagina and a portion of the endopelvic fascia have been removed to expose or show the deeper structures.

Pubis

Levator ani m.

Perineal membrane

External anal sphincter m.

Vagina

Anus

Urethra

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