What is adenomyosis, and what are its imaging characteristics?
Adenomyosis is the presence of ectopic endometrial tissue that develops and grows within the muscular wall of the uterus (i.e., the myometrium). It typically affects women of reproductive age, and symptoms may include severe menstrual cramps, bloating, dysmenorrhea, and menorrhagia. Uterine adenomyosis can be focal, diffuse, or even masslike (i.e., an adenomyoma) and mimic leiomyomas. Transvaginal US is typically used as the first line of imaging. US features of adenomyosis include heterogeneous, most commonly hypoechoic, myometrium with striations and an ill-defined endomyometrial junction. The uterus may appear asymmetric with globular thickening of a wall in focal adenomyosis. MRI can be very helpful to confirm this diagnosis. On MRI, adenomyosis is identified as thickening of the junctional zone (≥12 mm), often with presence of subcentimeter foci of T2-weighted (and sometimes T1-weighted) hyperintensity representing ectopic endometrial glands. Focal adenomyosis typically has indistinct margins and does not exert much, if any, mass effect upon adjacent structures.