Motion of the vaginal apex during strain and defecation

Although the main function of the suspensory ligaments of the vaginal apex is to prevent its descent toward the vaginal introitus, there remains limited information regarding its normal physiological motion. This study was aimed at quantifying the motion of the non-prolapsed vaginal apex during strain and defecation maneuvers.

This study represents a sub-analysis of a parent study that was aimed at evaluating rectal mobility with regard to obstructed defecation symptoms. Patients with normal apical vaginal support who had undergone MR defecography were entered into the study. For each patient, midsagittal images at rest, maximum strain, and maximum evacuation were utilized. The location of the cervicovaginal junction, S4-S5 intervertebral disc, sacral promontory, and hymen were identified. Vectors were calculated from each of these landmarks to the vaginal apex to compare vector angles and magnitudes across subjects.

Twelve patients were included in this study. At rest, the vagina extends from the hymen, which is inferior and posterior to the inferior symphysis pubis, to the vaginal apex at an angle of 45.2° ± 14.5° relative to the pubococcygeal line. This angle became more acute with strain and even more so during maximum evacuation (14.1° ± 9.0°, p < 0.001). Differences in the vector magnitude, although not statistically significant, showed a trend indicating shorter lengths with maximum evacuation.

The vaginal apex is a highly mobile structure demonstrating significantly more mobility during defecation compared with strain. The data obtained contradict the general perception that the vaginal apex is relatively fixed within the pelvis of normally supported women.