Technique development and measurement of cross-sectional area of the pubovisceral muscle on MRI scans of living women

  • Mariana MastelingEmail author
  • James A. Ashton-Miller
  • John O. L. DeLancey
Original Article


Introduction and hypothesis

Measurements of the anatomic cross-sectional area (CSA) of the pubovisceral muscle (PVM) in women are confounded by the difficulty of separating the muscle from the adjacent puborectal (PRM) and iliococcygeal (ICM) muscles when visualized in a plane orthogonal to the fiber direction. We tested the hypothesis that it might be possible to measure the PVM CSA within a defined region of interest based on magnetic resonance images (MRI).


MRI scans of 11 women with unilateral PVM tears and seven primiparous women with intact muscles following elective C-section were used to identify the PVM injury zone defined by the mean location of its boundaries with the adjacent intact PRM and ICM from existing anatomic reference points using 3D Slicer and ImageJ software. Then, from the 15 or more 2-mm transverse slices available, the slice with the maximum anatomic CSA of the left and right PVM was found in 24 primiparous women with bilaterally intact muscles who had delivered via C-section.


Mean [± standard deviation (SD)] of the maximum left or right PVM cross-section areas for the 24 women, measured by two different raters, was 1.25 ± 0.29 cm2 (range 0.75–1.86). The 5th, 50th, and 95th percentile values were 0.77, 1.23, and 1.80 cm2, respectively. Inter- and intrarater measurement repeatability intraclass correlation coefficients exceeded 0.89 and 0.90, respectively.


It is possible to use MRI to identify the volume of interest with the maximum anatomic cross section of the PVM belly while minimizing the inadvertent inclusion of adjacent PRM or ICM in that measurement.


Cross-sectional area MRI Pubovisceral muscle 



We thank Bing Xie, MD, for her support in the data analysis portion of this paper. We also thank Janis M. Miller, PhD, the principal investigator for the EMRLD project, for generously allowing us to use those MRI scans. Finally, we thank the women who were willing to be tested for these studies.


We are grateful for the Public Health Service and the Office for Research on Women and Gender Grants #P50 HD044406-07 and HD R01 38665 (JAAM & JOLD). MM was supported by the Fulbright Program for her masters dissertation research in Ann Arbor while a graduate student at the University of Porto, Portugal.

Compliance with ethical standards

Conflict of interest



  1. 1.
    DeLancey JOL. Whatʼs new in the functional anatomy of pelvic organ prolapse? Curr Opin Obstet Gynecol. 2016;28(5):420–9.CrossRefPubMedPubMedCentralGoogle Scholar
  2. 2.
    Kearney R, Sawhney R, DeLancey JOL. Levator Ani muscle anatomy evaluated by origin-insertion pairs. Obstet Gynecol. 2004;104(1):168–73.CrossRefPubMedPubMedCentralGoogle Scholar
  3. 3.
    Shafik A, Doss S, Asaad S. Etiology of the resting myoelectric activity of the levator ani muscle: Physioanatomic study with a new theory. World J Surg. 2003;27(3):309–14.CrossRefPubMedGoogle Scholar
  4. 4.
    DeLancey JO, Morgan DM, Fenner DE, Kearney R, Guire K, Miller JM, et al. Comparison of levator ani muscle defects and function in women with and without pelvic organ prolapse. Obstet Gynecol. 2007;109:295–302.CrossRefPubMedGoogle Scholar
  5. 5.
    Dietz HP, Simpson JM. Levator trauma is associated with pelvic organ prolapse. BJOG An Int J Obstet Gynaecol. 2008;115(8):979–84.CrossRefGoogle Scholar
  6. 6.
    Chen L, Ashton-Miller JA, DeLancey JOL. A 3D finite element model of anterior vaginal wall support to evaluate mechanisms underlying cystocele formation. J Biomech. 2009;42(10):1371–7.CrossRefPubMedPubMedCentralGoogle Scholar
  7. 7.
    Kim J, Betschart C, Ramanah R, Ashton-Miller JA, DeLancey JOL. Anatomy of the pubovisceral muscle origin: macroscopic and microscopic findings within the injury zone. Neurourol Urodyn. 2014;1–7.Google Scholar
  8. 8.
    Alt C, Hampel F, Hallsheidt P, Shon C, Schele B, Brocker K. 3T MRI-based measurements for the integrity of the female pelvic floor in 25 healthy nulliparous women. Neurourol Urodyn. 2016;35:218–23.CrossRefPubMedGoogle Scholar
  9. 9.
    Albrich SB, Laterza RM, Skala C, Salvatore S, Koelbl H, Naumann G. Impact of mode of delivery on levator morphology: a prospective observational study with three-dimensional ultrasound early in the postpartum period. 2011;51–61.Google Scholar
  10. 10.
    Enoka RM. Muscle strength and its development. New perspectives. Sports Med. 1988;6(3):146–68.CrossRefPubMedGoogle Scholar
  11. 11.
    Chen L, Hsu Y, Ashton-Miller JA, DeLancey JOL. Measurement of the pubic portion of the levator ani muscle in women with unilateral defects in 3-D models from MR images. Int J Gynecol Obstet. 2006;92(3):234–41.CrossRefGoogle Scholar
  12. 12.
    DeLancey JOL, Sørensen HC, Lewicky-Gaupp C, Smith TM. Comparison of the puborectal muscle on MRI in women with POP and levator ani defects with those with normal support and no defect. Int Urogynecol J. 2012;23(1):73–7.CrossRefPubMedGoogle Scholar
  13. 13.
    DeLancey JOL, Morgan DM, Fenner DE, Kearney R, Guire K, Miller JM, et al. Comparison of levator ani muscle defects and function in women with and without pelvic organ prolapse. Obstet Gynecol. 2007;109(2 Part 1):295–302.CrossRefPubMedGoogle Scholar
  14. 14.
    Lisa Kane Low, Ruth Zielinski, Yebin Tao, Andrzej Galecki, Catherine J. Brandon, Janis M. Miller. Predicting Birth-Related Levator Ani Tear Severity in Primiparous Women: Evaluating Maternal Recovery from Labor and Delivery (EMRLD Study). Open Am J Obstet Gynecol. 2014;04(06):266–278.CrossRefGoogle Scholar
  15. 15.
    Miller JM, Brandon C, Jacobson JA, Low LK, Zielinski R, Ashton-Miller J, et al. MRI findings in patients considered high risk for pelvic floor injury studied serially after vaginal childbirth. Am J Roentgenol. 2010;195(3):786–91.CrossRefGoogle Scholar
  16. 16.
    Rankin G, Stokes M. Reliability of assessment tools in rehabilitation: an illustration of appropriate statistical analyses. Clin Rehabil. 1998;12(3):187–99.CrossRefPubMedGoogle Scholar
  17. 17.
    Betschart C, Chen L, Ashton-Miller JA, DeLancey JOL. On pelvic reference lines and the MR evaluation of genital prolapse: a proposal for standardization using the pelvic inclination correction system. Int Urogynecol J. 2013;18(9):1199–216.Google Scholar
  18. 18.
    Betschart C, Kim J, Miller JM, Ashton-Miller JA, DeLancey JOL. Comparison of muscle fiber directions between different levator ani muscle subdivisions: in vivo MRI measurements in women. Int Urogynecol J Pelvic Floor Dysfunct. 2014;25(9):1263–8.CrossRefGoogle Scholar
  19. 19.
    Morris VC, Murray MP, DeLancey JOL. Ashton-miller JA. A comparison of the effect of age and levator ani and obturador internus muscle cross-sectional areas and volumes in nulliparous women. Neurourol Urodyn. 2012;31:481–6.CrossRefPubMedPubMedCentralGoogle Scholar
  20. 20.
    Ackerman AL, Lee UJ, Jellison FC, Tan N, Patel M, Raman SS, et al. MRI suggests increased tonicity of the levator ani in women with interstitial cystitis/bladder pain syndrome. Int Urogynecol J Pelvic Floor Dysfunct. 2016;27(1):77–83.CrossRefGoogle Scholar
  21. 21.
    Hoyte L, Jakab M, Warfield SK, Shott S, Flesh G, Fielding JR. Levator ani thickness variations in symptomatic and asymptomatic women using magnetic resonance-based 3-dimensional color mapping. Am J Obstet Gynecol. 2004;191(3):856–61.CrossRefPubMedGoogle Scholar
  22. 22.
    Fielding JR, Dumanli H, Schreyer AG, Okuda S, Gering DT, Zou KH, et al. MR-based three-dimensional modeling of the normal pelvic floor in women: quantification of muscle mass. Am J Roentgenol. 2000;174(3):657–60.CrossRefGoogle Scholar
  23. 23.
    Sasaki T, Yoshimura N, Hashizume H, Yamada H, Oka H, Matsudaira K, et al. MRI-defined paraspinal muscle morphology in Japanese population: the Wakayama spine study. PLoS One. 2017;12(11):1–15.Google Scholar
  24. 24.
    Kim T, Sridharan I, Ma Y, Zhu B, Chi N, Kobak W, et al. Identifying distinct nanoscopic features of native collagen fibrils towards early diagnosis of pelvic organ prolapse. Nanomedicine. 2015;12(3):667–75.CrossRefPubMedGoogle Scholar
  25. 25.
    Trowbridge ER, Wei JT, Fenner DE, Ashton-Miller JA, DeLancey JOL. Effects of aging on lower urinary tract and pelvic floor function in nulliparous women. Obstet Gynecol. 2007;109(3):715–20.CrossRefPubMedGoogle Scholar
  26. 26.
    Lebendige RK. Anatomie der Vagina. Geburtshilfe Frauenheilkd. 1966;26:1213–23.Google Scholar

Copyright information

© The International Urogynecological Association 2018

Authors and Affiliations

  1. 1.Department of Mechanical EngineeringUniversity of MichiganAnn ArborUSA
  2. 2.Department of Obstetrics and GynecologyUniversity of MichiganAnn ArborUSA

Personalised recommendations