MRI of the Female Pelvis

This webpage presents the anatomical structures found on female pelvis MRI.

Magnetic resonance imaging or MRI of the female pelvis offers a unique display of the pelvic anatomy, including a woman’s ovaries, uterus, and fallopian tubes. 

MRI is a valuable technique in diagnosing or staging anomalies or conditions in the female pelvic region. Unlike sonography or computed tomography (CT), MRI offers distinct advantages in staging cervical and endometrial carcinoma(1). 

MRI’s main advantages are its ability to depict tumor and provide great tissue contrast between the tumor and surrounding normal tissue. Other advantages of MRI include the following(2):

  • Non-invasive procedure
  • Independent of ionizing radiation 
  • Excellent soft-tissue contrast resolution
  • Multidirectional imaging
  • Simultaneous imaging of multiple sections
  • Visualization of blood vessels without contrast injection

Imaging of the Female Pelvic Region

MRI complements sonography and CT in further refining anatomic details and allowing the display of disease in more detail(3).  

The axial (horizontal) image of the female pelvis shows the ovaries, uterus, ligament, uterine tubes, vaginal cavity, and other internal organs. 

The sagittal (longitudinal) image of the female pelvis shows anatomical structures. These structures include the urinary system, genital organs, muscles, veins, nerves, arteries, and pelvic measurements.

The uterine zonal anatomy and temporal changes under hormonal stimuli are well displayed on the T2-weighted images(4). These images are basic pulse sequences in MRI that provide the best depiction of a disease(5).  

MRI accurately demonstrates benign and malignant uterine neoplasms. However, this imaging tool cannot diagnose the tumor type(6). 

The primary MRI techniques related to the female pelvis include(7):

  • The evaluation of anatomic variants or reproductive dysfunction
  • Specific obstetrical applications
  • Oncologic evaluation and tumor staging
  • Problem-solving (the characterization of abnormalities detected by ultrasound)
  • The evaluation of urethral disease

Anatomy of the Female Pelvis

Knowledge of the female pelvic anatomy is vital to the step-by-step approach in evaluating an unknown pelvic mass. The first step is assessing the mass’ site of origin and its location in relation to the peritoneal cavity and the extraperitoneal spaces.

This information is necessary to suggest the correct diagnosis, narrow the differential possibilities, and select the optimal surgical approach.

Like the abdomen, the pelvis is divided into two main compartments: the peritoneal cavity and subperitoneal space(8).  

The peritoneum separates the two spaces, with each compartment as a continuous space. The subperitoneal space encloses all of the abdominal and pelvic organs, ligaments, vessels, nerves, and lymphatics.

The peritoneal cavity is situated between the thin layers of the visceral and parietal peritoneum (analogs to the pleura). This cavity is a potential space without any organs(9). 

The visceral peritoneum lines the surfaces of various organs to form their serous membrane (serosa). Meanwhile, the parietal peritoneum lines the body cavity’s wall. 

The organs in the subperitoneal space are located deep into the peritoneum. These organs include the ureters, urinary bladder, uterine corpus and cervix, mid and lower rectum, and vagina.

Female Pelvis Pathology

Uterine Leiomyomas

Leiomyoma (benign uterine neoplasms) is the most common tumor of the female genital tract. These tumors are based on their location within the uterine corpus as either submucosal, intramural, or subserosal(10). 

Although most women are asymptomatic, the most common leiomyoma symptom is bleeding. Transvaginal ultrasound has been demonstrated to be as efficient as MRI in detecting the presence of myomas(11). 

However, MRI is a superior modality in mapping individual myomas, especially with larger uteri and the presence of a large number of myomas(12). 

The MRI shows an enlarged uterus containing leiomyomas with an abnormal contour. On T2-weighted images, leiomyomas appear as sharply marginated lesions of low signal intensity relative to the myometrium.

Endometrial Carcinoma

Endometrial carcinoma is a common type of cancer in the uterus. In 75% to 90% of cases, patients present with abnormal uterine bleeding(13). 

MRI has proven to be an essential tool in the staging of known endometrial carcinoma(14). This tool can differentiate between superficial and deep muscle-invasive tumors using combined T2-weighted imaging and contrast-enhanced MRI.

Additionally, MRI is superior to ultrasound and CT in assessing cervical extension, myometrial invasion, and nodal involvement(15). 

Endometrial carcinomas appear isointense to the endometrium and myometrium on T1-weighted images. Meanwhile, the signal intensity is commonly hyperintense on T2-weighted images(16). 

Hemorrhagic Ovarian Cyst 

MRI has high contrast resolution and tissue characterization capabilities that help characterize echogenic adnexal masses initially detected by ultrasound(17). 

The accuracy of MRI in identifying lesions, including hemorrhagic cysts and endometriomas, is higher than with transvaginal ultrasound imaging(18). 

Hemorrhagic cysts should remain of relatively high signal on T1-weighted images with fat suppression to help doctors differentiate them from dermoid cysts. 

Hemorrhagic cysts may also have thicker walls than simple cysts and may show wall enhancement on postcontrast images(19).


19 Sources

References

  1. Hricak, H. (1986). MRI of the female pelvis: a review. American Journal of Roentgenology, 146(6), 1115-1122.
  2. Hricak, H. op. cit.
  3. Ibid.
  4. Ibid.
  5. Chen Y., Almarzouqi S.J., Morgan M.L., Lee A.G. (2018) T2-Weighted Image. In: Schmidt-Erfurth U., Kohnen T. (eds) Encyclopedia of Ophthalmology. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-540-69000-9_1229
  6. Hricak, H. op. cit.
  7. Kennedy, A. M., Gilfeather, M. R., & Woodward, P. J. (1999). MRI of the female pelvis. Seminars in ultrasound, CT, and MR, 20(4), 214–230. https://doi.org/10.1016/s0887-2171(99)90067-7
  8. Meyers, M. A., Charnsangavej, C., & Oliphant, M. (2010). Meyers’ dynamic radiology of the abdomen: normal and pathologic anatomy. Springer Science & Business Media.
  9. Pannu, H. K., & Oliphant, M. (2015). The subperitoneal space and peritoneal cavity: basic concepts. Abdominal imaging, 40(7), 2710-2722.
  10. Hricak, H. op. cit.
  11. Dueholm, M., Lundorf, E., Hansen, E. S., Ledertoug, S., & Olesen, F. (2002). Accuracy of magnetic resonance imaging and transvaginal ultrasonography in the diagnosis, mapping, and measurement of uterine myomas. American journal of obstetrics and gynecology, 186(3), 409-415.
  12. Ibid.
  13. Manfredi R, Gui B, Maresca G, et al. Endometrial cancer: Magnetic resonance imaging. Abdom Imaging. 2005;30:626-636.
  14. Yamashita Y, Mizutani H, Torashima M, et al. Assessment of myometrial invasion by endometrial carcinoma: Transvaginal sonography vs contrast-enhanced MR imaging. AJR Am J Roentgenol.1993;161:595-599.
  15. Ibid. 
  16. Ibid.
  17. Ibid.
  18. Mohaghegh, P., & Rockall, A. G. (2012). Imaging strategy for early ovarian cancer: characterization of adnexal masses with conventional and advanced imaging techniques. Radiographics, 32(6), 1751-1773.
  19. Schwartz LB, Panageas E, Lange R, et al. Female pelvis: Impact of MR imaging on treatment decisions and net cost analysis. Radiology. 1994;192:55-60.

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