MR imaging of the uterus: low-signal-intensity abnormalities of the endometrium and endometrial cavity.

T2-weighted magnetic resonance (MR) images showing focal areas of low signal intensity involving the endometrium or endometrial cavity were analyzed retrospectively in 28 women. The causes of the hypointense foci were disclosed histologically in 25 patients and by follow-up MR examinations in the other 3. The low signal intensity foci were due to submucosal leiomyoma (11 patients), blood clot (7 patients), endometrial carcinoma (4 patients), early intrauterine pregnancy (3 patients), retained products of conception (2 patients), and endometrial hamartoma (1 patient). The correct diagnosis was made on the basis of MR findings alone in 9 of the 11 submucosal leiomyomas. MR findings were nonspecific in the remainder of the cases. The results indicate that, on MR images, hypointense foci within the endometrium or endometrial cavity can arise from a variety of causes. Often, a specific diagnosis is not possible, and correlation with clinical history is essential.