Uterine adenomyosis: endovaginal US and MR imaging features with histopathologic correlation.

Uterine adenomyosis is a common gynecologic condition that is characterized by the presence of heterotopic endometrial glands and stroma in the myometrium with adjacent smooth muscle hyperplasia. The histopathologic features of adenomyosis are varied and contribute to its imaging appearance. The accompanying smooth muscle hyperplasia produces the typical gross appearance of adenomyosis and corresponds to areas of decreased echogenicity at endovaginal ultrasonography (US) and areas of decreased signal intensity at magnetic resonance (MR) imaging. Endovaginal US also shows heterogeneity of the myometrial echotexture, which corresponds to small echogenic islands of heterotopic endometrial tissue surrounded by the hypoechoic smooth muscle. On T2-weighted MR images, bright foci are seen in areas of abnormal low signal intensity within the myometrium in approximately 50% of patients. These foci correspond to islands of heterotopic endometrial tissue, cystic dilatation of heterotopic glands, or hemorrhagic foci. With the advent of high-resolution imaging techniques, signs associated with the presence of heterotopic endometrial tissue are being detected with increasing frequency. These signs include myometrial cysts, myometrial nodules, linear striations, pseudowidening of the endometrium, and poor definition of the endomyometrial junction. Pitfalls in diagnosis of uterine adenomyosis include leiomyoma, endometrial carcinoma, myometrial contractions, and muscular hypertrophy.