“Vaginal Shape at Resting Pelvic MRI: Predictor of Pelvic Floor Weakness?”

Tillack AA, et al. Clin Imag 2015;39:285-288.

Cora Huit

Pelvic PT distance journal club Sept 2, 2015

Aim: The goal of this study was to determine if vaginal shape was related to pelvic floor weakness.

Design: Population: This study was done retrospectively using images from a radiology database of 32 women who were referred for pelvic floor imaging between 1998 and 2007. The same data was collected from the radiology database for a control group of 44 women who were referred for pelvic floor imaging for the following health concerns: fibroids, adnexal mass, nongynecological caner or mass, pelvic pain, endometrial evaluation, gynecological caner and retrovaginal fistula. 

Imaging: A normal vaginal shape was described as a vagina with an “H” shape or a horizontal shape through a cross section image. Vaginal shape is largely linked to an individual’s paracolpium, which is a dense area of endopelvic fascia. Pubocervical fascia helps support the bladder and rectovaginal fascia supports the rectum.  Damage to the paracolpium is a factor that can lead to pelvic floor weakness, as well as, changed vaginal shape. Pregnancy and childbirth are common factors in altering paravaginal fascia.

 Axial T2-weighted MR images were used to view and assess vaginal shape for patients in the supine position. These images were taken through the vagina using a pelvic phased array coil. The researchers divided the regions of the pelvic floor into anterior, middle and posterior compartments, which represents the bladder, uterus and bowel respectively.

Imaging evaluation: Two readers with 11 and 12 years of experience reviewed the images after they had been randomized. The readers were blinded to a patient’s diagnosis. Readers were to determine if vaginal shape was conventional (H-shaped) or distorted (M-shaped or W-shaped).

Hypothesis: It was hypothesized that M-shaped vaginas would correlate with posterior weakness and that W-shaped vaginas would correlate with anterior compartment weakness. Researchers further hypothesized that an abnormal vaginal shape found on the T2-axial pelvic MR image would correspond to pelvic floor weakness.

Results: The readers determined that out of the 32 images of women, who were referred for imaging due to pelvic floor weakness, 10 patients had isolated anterior weakness, 6 had isolated posterior weakness and 16 had weakness in more than one area. Interobserver agreement was fair. Statistical analysis showed that pelvic floor weakness and distorted vaginal shape was statistically significant for both readers.

            The first reader established that 70% of the patients with anterior compartment weakness had a W-shape, but also stated that 7 out of 44 patients with no pelvic floor weakness had a W-shape, 11 out of 16 with multicompartmental weakness had a W-shape and 2 of 6 patients with isolated posterior compartment weakness had a W-shape. The second reader established that 40% of patient with anterior weakness had a W-shape, as well as, 2 patients from the control group, and 6 of 16 patients with multicompartmental weakness. M-shaped vaginal weakness for the first reader was established as the following: 1in 10 patients with anterior weakness, 4 of 44 control patients, 8 of 16 patients with multicompartmental weakens and 1 of 6 patients with isolated posterior weakness. M-shaped vaginal weakness for the second reader was established as the following: 0 out of 10 patients with anterior weakness, 1 of 44 control patients, 3 of 16 patients with multicompartmental weakness and 1 of 6 patients with isolated posterior weakness.

Discussion: Pelvic floor weakness often goes undiagnosed for a variety of reasons. Issues that arise from weakness of the pelvic floor can be very disruptive to women’s lives and affects them physically, emotional and socially. It was the hope of researchers that if vaginal shape could be a diagnostic tool in determining pelvic floor weakness then treatment could be provided to assist these women after having imaging. The study results showed that, while MR imaging used to evaluate vaginal shape could help be a predicator of possible pelvic floor weakness, it was not diagnostic. Reader agreement in the study was fair, with one reader being more likely to diagnose a true positive than a true negative and the other read being more likely to diagnose a true negative than a true positive. Also, it was found that M-shape and W-shape was not a parallel to anterior and posterior compartment weakness.

Weaknesses of the study: One weakness of this study was the selection process for the control group. As stated previously, pelvic floor weakness is usually under diagnosed. Therefore, it is possible that women in the control group had some pelvic floor weakness that was not available in their clinical information. Also, the images collected during the MR imagining were a part of routine clinical imaging and were not directed at the axis of the vagina, which may have yielded better imaging and better reader evaluation.

Strengths of the study: Only two readers were used to determine vaginal shape because this is the common clinical scenario when patients are present for screenings.

Conclusion: MR imaging may be used to help propose possible pelvic floor weakness but due to the lack of reader agreement in this particular study, there was no fixed correlation between vaginal shape and pelvic floor weakness.

See additional editorial with more references

Nygaard I. Editorial  Pelvic Floor Recovery After Childbirth Obstect and Gynecol 2015;125(3):529-530.