Anything that increases the specific gravity of the uterus will make it sink somewhat lower in the pelvis. Subinvolution, congestion from inflammation, or retroflexion may do this. In such cases, however, the prolapse never becomes extreme, rarely extending beyond a slight sinking of the uterus.
In most cases uterine prolapse takes place slowly. Sometimes many years are necessary for the development of complete prolapse. The equilibrium of the pelvic contents is destroyed by one of the causes already mentioned. The uterus falls through a certain distance before the uterine ligaments become suspensory. Then, however, its further descent is impeded.
If the original cause continues to act, the uterine ligaments become stretched and the descent of the uterus gradually progresses, impeded to a varying degree also by the retentive power of the abdomen and the cellular tissue and other pelvic attachments.
As the uterus descends, the vaginal walls attached at the cervix are dragged down with it, so that when the prolapse becomes complete the vagina is turned inside out ([Fig. 67]).
When the perineum has been injured so that the lower portion of the vagina loses its support and the equilibrium of the pelvic contents is destroyed, two distinct phenomena occur: The uterus falls as already described, and at the same time the lower part of the vagina begins to fall, so that there appear a prolapse of the anterior vaginal wall, or a cystocele, and a prolapse of the posterior wall, or a rectocele. The condition finally produced will depend upon which prolapse takes place the more rapidly—that of the vagina or that of the uterus.
Fig. 67.—Complete prolapse of the uterus.
If the prolapse of the lower vagina progresses faster than that of the uterus, then the vagina will begin to drag upon the cervix, to which it is attached, and under these circumstances the uterus will be subjected to two downward forces—intra-abdominal pressure from above, and traction of the vaginal walls acting from below.
Fig. 68.—Prolapse of the vagina and the vaginal cervix, with great elongation of the supra-vaginal cervix.