Adenomyosis is the presence of ectopic endometrial glands from the basal layer of the endometrium within the myometrium, often associated with myometrial hyperplasia. It is a common gynecologic disorder that most commonly affects premenopausal women. Symptoms are nonspecifc and include pelvic pain, dysmenorrhea, menorrhagia, and abnormal uterine bleeding. Al-though adenomyosis is typically a diffuse process, focal areas of involvement are also seen. It is these focal lesions that are often mistaken for leiomyomas. It is important to differentiate between them, as their treatments vary greatly. Although gonadotropin-releasing hormone analog therapy or endometrial ablation can be performed, the defnitive treatment for severe cases of adenomyosis is ultimately hysterectomy. With the advent of more conservative therapies such as embolization therapy, MRI may play a role in monitoring treatment response.
Studies have shown that MRI is superior to ultrasound for the diagnosis of adenomyosis. The characteristic appearance of adenomyosis on MRI is diffuse thickening (>12 mm) of the junctional zone. This is most evident on T2W sequences and corresponds to the smooth muscle hyperplasia associated with the ectopic tissue. A junctional zone ≤8 mm virtually excludes the disease, whereas a width of 9 to 11 mm is equivocal. Other fndings that may suggest the diagnosis include poorly defned margins of the junctional zone and foci of high signal intensity on T1W or T2W sequences that indicate the presence of endometrial cysts (Figure 11). The foci of high signal may represent ectopic endometrium, cystically dilated endometrial glands, or hemorrhage.[27,28,29] Contrast administration has been shown to be of very little beneft in the diagnosis of adenomyosis.
Diffuse adenomyosis. This sagittal fat-suppressed T2-weighted image shows diffuse thickening of the low-T2-signal junctional zone (arrows). Scattered T2 high signal foci (arrowheads) are consistent with endometrial cysts.
Distinguishing between focal adenomyosis and leiomyomas is reliably achieved with MRI, and we now know that these conditions often coexist. Unlike leiomyomas, a focal area of adenomyosis will have indistinct margins and extend subjacent to the myometrium. The signal characteristics will otherwise be the same as with the diffuse form of the disease. Treatment implications for focal adenomyosis and leiomyoma differ, however, so accurate diagnosis is important.
Appl Radiol. 2008;37(1):9-24. © 2008 Anderson Publishing, Ltd.
Cite this: Imaging the Female Pelvis: When Should MRI be Considered? - Medscape - Jan 01, 2008.