Fig. 3.13 Lateral view of the pelvis showing the relationships of the puborectalis, iliococcygeus and pelvic floor structures after removal of the ischium below the spine and sacrospinous ligament (SSL) (EAS, external anal sphincter). The bladder and vagina have been cut in the midline, yet the rectum left intact. Note how the endopelvic fascial ‘pillars’ hold the vaginal wall dorsally, preventing its downward protrusion.
Fig. 3.14 Midvaginal posterior prolapse that protrudes through the introitus despite a normally supported perineal
Fig. 3.15 Levator ani muscles seen from below the edge of the perineal membrane (urogenital diaphragm) can be seen on the left of the specimen.
Fig. 3.16 Position of the perineal membrane and itsassociated components of the striated urogenital sphincter, the compressor urethrae and the urethrovaginal sphincter.
The posterior vaginal wall is supported by connections
between the vagina, the bony pelvis and the levator ani
muscles (Smith et al 1989b). The lower one-third of the
vagina is fused with the perineal body (Fig. 3.11), which
is the attachment between the perineal membranes on
either side. This connection prevents downward descent
of the rectum in this region.
If the fi bres that connect one side with the other
rupture then the bowel may protrude downward resulting
in a posterior vaginal wall prolapse (Fig. 3.12).
The midposterior vaginal wall is connected to the
inside of the levator ani muscles by sheets of endopelvic
fascia (Fig. 3.13). These connections prevent ventral
movement of the vagina during increases in abdominal
pressure. The medial most aspect of these paired sheets
is referred to as the rectal pillars.
In the upper one-third of the vagina, the vaginal wall
is connected laterally by the paracolpium. In this region
there is a single attachment to the vagina, and a separate
system for the anterior and posterior vaginal walls does
not exist. Therefore when abdominal pressure forces the
vaginal wall downward towards the introitus, attachments
between the posterior vagina and the levator
muscles prevent this downward movement.
The uppermost area of the posterior vagina is suspended,
and descent of this area is usually associated
with the clinical problem of uterine and/or apical prolapse.
The lateral connections of the midvagina hold this
portion of the vagina in place and prevent a midvaginal
posterior prolapse (Fig. 3.14). The multiple connections
of the perineal body to the levator muscles and the
pelvic sidewall (Figs 3.15 and 3.16) prevent a low posterior
prolapse from descending downward through the
opening of the vagina (the urogenital hiatus and the
levator ani muscles). Defects in the support at the level
of the perineal body most frequently occur during
vaginal delivery and are the most common type of posterior
vaginal wall support problem.
Labels: CHAPTER 2