Multiple observational studies have found an association of uterine prolapse with uterine retroversion. Mechanisms proposed to explain this apparent association assume that the cervix of a retroverted uterus will usually insert at the apex of the vagina with resultant alignment of the cervix with the vagina. To the best of our knowledge no data to support this assumption had been gathered previously so we measured the angle of version of the cervix with the vagina in a series of female abdominopelvic and pelvic CT scans and pelvic MRI scans to confirm or exclude this positioning.

The angle of the axis of the cervix with the axis of the vagina was measured by two readers on T2 sagittal images of the pelvic MRI scans and the sagittal reconstructions of the pelvic and abdominopelvic CT scans on 323 scans performed for clinical purposes at our institution. In addition, one reader recorded the anatomic relations that differed with insertion site and version of the uterus.

44 of 49 retroverted uteri (89.8 %) inserted at the vaginal apex.13 of 274 anteverted uteri (4.7 %) inserted at the vaginal apex. This difference was found to be statistically significant (p < 0.05) by the Chi square test. This data provides robust support for the hypothesis that most retroverted uteri insert at the apex of the vagina.

The urinary bladder, vaginal walls and rectum were noted to be inferiorly related to anterior anteverted uteri. Only the vaginal lumen and the rectum at a shallow oblique angle were inferiorly related to apical retroverted uteri. Hence, adjacent structures appear to provide far less support for the uterus in apical retroversion than in anterior anteversion.