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Reproductive/Endocrine Imaging

E2422. Vaginal Anatomy on MRI: New Information Obtained Using Distention

Appelbaum A1,  Zuber J1,2,  Levi-D'Ancona R2,  Peregrin-Alvarez I2,  Cohen H.2 1. Memphis Veterans Affairs Medical Center, Memphis, TN; 2. University of Tennessee Health Sciences Center, Memphis, TN

Address correspondence to A. Appelbaum (alanappelbaum@hotmail.com)

Objective: On pelvic MRI scans performed with the vagina distended by contrast gel, the vagina appears to have three anatomic zones; a superficial sphincteric zone, a central wedge-shape transition zone, and a deep, expanded forniceal zone. The purpose of this study is to confirm this configuration and to demonstrate other aspects of vaginal anatomy.

Materials and Methods: After institutional review board approval was obtained, 100 consecutive female pelvic MRI scans using contrast gel to obtain vaginal distention, performed for clinical purposes between January 2007 and February 2015 were retrospectively reviewed. The images were observed for the three-zone configuration. Anteroposterior (AP) diameter measurements were taken in 81 cases in the proximal, mid, and distal sphincteric zones (S1–S3) and transition zones (T1–T3) and in the anterior fornix (F1), cervical os (F2), and posterior fornix (F3) or their expected locations. Mean ± SD values were calculated at each site. Adjacent sites were compared using paired t tests. The position of the uterus and configuration of the fornix was noted in all cases.

Results: The three-zone configuration was observed in all cases but one where the transition zone and forniceal zones were compressed by an enlarged uterus. Statistically significant measurement increases of AP diameters occurred at all expected sites (S3–T1, p < 0.001; T1–T2, p < 0.001; T2–T3, p < 0.001; T3–F1, p = 0.021). No significant change occurred between the mid and distal sphincteric zone, as expected. Statistically significant measurement decreases occurred at all expected sites (S1–S2, p < 0.001; F1–F2, p < 0.001). Thus, the findings on image review were confirmed by measurement. The cervix can enter the vagina at two different sites, the anterosuperior wall and the apex. All anteverted uteri entered the vagina at the anterosuperior wall, 84 cases (79.6%). All retroverted and neutrally positioned uteri entered the vagina at the apex, 19 cases (20.4%). In mild anteversion, retroversion, or in the neutral position, the anterior and posterior fornices were always present. The posterior fornix was usually longer and wider than the anterior fornix. As the uterus rotates anteriorly or posteriorly, the fornices diminish in size. In severe retroversion or anteversion, the anterior fornix, posterior fornix, or both can be absent. After hysterectomy, the deep zone of the vagina takes on an ovoid configuration with no remnant of the fornices.

Conclusion: The distended vagina has a three-zone configuration consisting of a narrow sphincteric zone, a wedge-shape transition zone, and a variable deep expanded forniceal zone. The expanded configuration of the vagina may facilitate entrance of the fetus into the vagina during parturition and may have implications for fertility methods, intravaginal medication administration, and vaginal irrigation. The three zones of vaginal distention correspond to the three levels of vaginal support described by DeLancey et al. [1]. Anteverted and retroverted uteri are anatomically distinct as they have different sites of entry into the vagina. The fornices vary in size with the position of the uterus and can be absent. Reference 1. DeLancey JO. Anatomic aspects of vaginal eversion after hysterectomy. Am J Obstet Gynecol 1992; 166:1717–1724