Imaging the Female Pelvis: When Should MRI be Considered?

Jennifer Hubert, MD; Diane Bergin, MD


Appl Radiol. 2008;37(1):9-24. 

In This Article

Adnexal Masses

In the premenopausal woman, the ovaries are typically well evaluated by ultrasound. When evaluating an adnexal mass on ultrasound, the diagnostic challenges that may arise include accurately localizing the mass, determining whether or not it is ovarian in origin, and, when complex, whether it is defnitively benign or malignant. Many adnexal masses are benign and, when indicated, can be treated surgically by laparoscopic technique. Complex echogenic adnexal lesions on ultrasound may represent hemorrhagic cysts, endometrioma, dermoids, or ovarian neoplasms. If a cystic adnexal mass >5 cm in a premenopausal woman or >3 cm in a postmenopausal woman persists or increases in size on follow-up ultrasound, MRI should be considered so that malignancy can be excluded.[5,6,7,8] MRI should also be considered when a solid or solid cystic adnexal lesion with internal color flow is detected by ultrasound. MRI has an overall accuracy of 91% to 93% in the characterization of adnexal masses as benign or malignant. In these circumstances, it has been found that the use of MRI is cost-effective in that it reduces unnecessary surgical procedures.

A simple unilocular ovarian cyst is not an indication for MRI, as it is a common incidental fnding in both pre- and postmenopausal women. These cysts are well evaluated by ultrasound. However, the postmenopausal ovary tends to contain fewer cysts of smaller size. When they are <3 cm in size with a wall ≤3 mm and have the characteristic appearance of low T1 and high T2 signal intensity, these cysts can be considered benign in both populations. Studies that specifcally examined the premenopausal ovary have shown that the risk of malignancy for unilocular cysts <5 cm in an asymptomatic woman approaches zero.


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