Adenomyosis is a non-neoplastic condition in which ectopic endometrium invades the myometrium of the uterus. Diagnosis relying on clinical symptoms is difficult, because the symptoms are nonspecific (dysmenorrhea, menorrhagia). Both transvaginal sonography (TVS) and MRI of the pelvis are useful in detecting this condition. MRI has a high sensitivity (78-88%) and specificity (67-93%) for diagnosing adenomyosis. The reported sensitivity and specificity of TVS are 53-89% and 67-98%. MRI should be performed whenTVS is equivocal.
On MRI, adenomyosis demonstrates either diffuse or focal thickening of the junctional zone. On T2 images, there are low signal areas corresponding to muscle hyperplasia and increased sign areas, which represent ectopic endometrial tissue. When hemorrhage occurs, T1 images show foci of increased signal. A junctional zone thickness > 12 mm is diagnostic of adenomyosis on MRI. Generally, the uterus is enlarged as well. There is also a focal form (adenomyoma) which presents as an ovoid, T2 dark mass often situated in the junctional zone.
On TVS, the uterus is globular in shape and there is loss of the endometrial/myometrial junction. Often, it is difficult to measure the endometrium. Myometrial cysts in the subendometrial region, “sawtooth” shadowing from the myometrium,and asymmetric uterine wall thickening are also imaging characteristics seen on TVS. Sometimes the patient experiences pain with ultrasound palpation of the uterus. (Fibroids are less likely to be painful). Adenomyomas on TVS are poorly defined, echogenic masses. Also on TVS, adenomyosis may present as asymmetric thickening of the myometrium, no mass effect on the endometrium and increased vascularity within the affected portion of the uterus. Fibroids are the most common lesion that resemble adenomyosis. Fibroids are less likely to be painful than is adenomyosis. A correct pre-operative diagnosis is necessary since surgical treatment for adenomyosis is hormone therapy or hysterectomy and the treatment for leiomyoma could be embolization or myomectomy. In MRI, fibroids are hypointense on T2 images, and tend to be round, rather than elliptical like a focal adenomyoma. There is mass effect produced by fibroids, but not usually with adenomyosis. Fibroids on TVS show discrete shadowing and peripheral draping of vessels, which are not features of adenomyosis.
SagittalT2- weighted image shows an illdefined myometrial lesion of low signal intensity in the anterior mypmetrium. Innumerable hyperintense foci (arrows) are embedded in the lesion.
Marked enlargement of the junctional zone (arrows)
Enlargement of uterus and heterogeneous myometrium in patient with adenomyosis
Transvaginal US image demonstrates an echogenic mass with ill-defined borders (arrows), findings cEnlargement of uterus and heterogeneous myometrium in patient with adenomyosisharacteric of an adenomyoma.
Tiny subendometrial cysts (arrow) representing dilated glands of ectopic endometrium, highly specific for diffuse adenomyosis.
Reference: Tamai K, Togashi K, Ito T, et al. MR imaging findings of adenomyosis: in correlation with histopathologic features and diagnostic pitfalls. RadioGraphics 2005; 25:21-40. Reproduced with permission.