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Pelvic Floor Levator Hiatus Measurements: MRI Versus Ultrasound

Nardos, Rahel MD, MCR*; Thurmond, Amy MD; Holland, Amanda MPH; Gregory, W. Thomas MD

Female Pelvic Medicine & Reconstructive Surgery: July/August 2014 - Volume 20 - Issue 4 - p 216–221
doi: 10.1097/SPV.0000000000000079
Original Articles

Objective: The objective of this study is to compare levator hiatus measurements between pelvic magnetic resonance imaging (MRI) and pelvic ultrasound (US) imaging modalities.

Methods: We performed pelvic MRI and 3-dimensional US in 37 asymptomatic nulliparous women. For the MRI protocols, we performed axial and sagittal sequences at rest. We then obtained sagittal sequences during Kegel squeeze and Valsalva maneuvers. Blinded to the findings of the MRI, we obtained 3-dimensional pelvic US images using a perineal approach at rest, Kegel and Valsalva maneuvers. Finally, we measured the levator hiatus in both sagittal and axial planes.

Results: For the resting sagittal measurements, the mean levator hiatus measurement using MRI (5.0 cm; SD, 0.8) is significantly greater than that using US (4.4 cm; SD, 0.6; P < 0.05). Although the absolute mean levator measurements between the 2 modalities are significantly different, this difference is not influenced by the magnitude of the measurements as noted in Bland-Altman plots of the limits of agreement.

Conclusions: We found that the MRI measurements obtained from the sagittal images were consistently greater than the corresponding US images. In contrast, there was not the same consistency of difference between MRI and US for the axial images. This suggests possible variation in acquisition planes for axial images or interpretation of landmarks for the sagittal images.

Sagittal measurements of the levator hiatus obtained using 2D MRI are slightly greater than the same measurements made using 3D transperineal ultrasound. Comparisons of levator hiatus measurements in the axial plane demonstrate mixed results.

From the *Division of Female Pelvic Medicine and Reconstructive Surgery, Department of Obstetrics and Gynecology, Oregon Health & Science University, Kaiser Permanente; †Department of Obstetrics and Gynecology, and ‡Division of Female Pelvic Medicine and Reconstructive Surgery, Department of Obstetrics and Gynecology, Oregon Health & Science University, Portland, OR.

Reprints: Rahel Nardos, MD, MCR, Division of Female Pelvic Medicine and Reconstructive Surgery, Department of Obstetrics and Gynecology, Oregon Health & Science University, Kaiser Permanente, L466, 3181 SW, Sam Jackson Park Rd, Portland, OR 97239. E-mail: nardosr@ohsu.edu.

The authors have declared they have no conflicts of interest.

Sources of Support: NIH (NICHD); contract grant number: HD049541; Oregon Clinical and Translational Research Institute; National Center for Research Resources: UL1 RR024140; NIH Roadmap for Medical Research.

© 2014 by Lippincott Williams & Wilkins