MRI appearance of adenomyosis

Clinical History

Obstetric history: TPAL 0-0-1-0.
Gynecologic history: laparotomic excision of a subserosal uterine fibroid 8 years ago; conization and radiotherapy for an invasive carcinoma of the uterine cervix 7 years ago.
Current symptoms: metrorrhagia and sideropenic anemia.

Imaging Findings

MRI shows smooth enlargement of the fundus and posterior hemisphere of the uterus, which appears inhomogeneous on both T1w and T2w images.
T2w MRI shows a large hypointense area deeply extending into the myometrium and containing small cysts; the junctional zone (JZ) is not visible along the fundus and the posterior aspect of the uterine body. A small endometrial polyp is also detected. The uterine cavity is filled by loss signal intensity material consistent with protinaceous material (Fig. 1a-c).
T1w MRI evidences many tiny hyperintense foci (Fig. 1d).
T2*w MRI shows void signal foci (Fig. 1e).
T1w FS MRI: pre-contrast images confirm presence of hyperintense spots, consistent with hemorrhagic foci; the inhomogeneous area evidenced on T2 images less enhances than the remaining myometrium. The endometrial polyp is also shown (Fig. 2).

Discussion

Adenomyosis consists with ectopic localization, diffuse or focal, of endometrial glands and stroma into the myometrium; the ectopic endometrium induces hypertrophy and hyperplasia of the myometrium, causing uterine enlargement [1].

Incidence of adenomyosis is unknown because of the lack of standard diagnostic criteria and bias from pathological diagnosis; diagnosis rate at hysterectomy ranges from 20% to 30%[1]. Estrogen exposure, early menarche, short menstrual cycle, parity and prior uterine surgery are considered risk factors [1].

Pathogenic hypotheses comprise invagination of the endometrial basalis (causes by myometrial weakness or altered immunologic activity or hormone mediate), de novo development from müllerian rests, invagination of basalis endometrium through myometrial lymphatics, myometrial seeding of displaced bone marrow steam cells [1]; an uterine auto-traumatization in non-pregnant uterus due to peristalsis and hyperperistalsis is also suggested for pathogenesis [2].

Adenomyosis is often associated with hormone-dependent pelvic lesions (myoma, deep pelvic endometriosis, polyps, or endometrial hyperplasia)[3].

Symptoms include heavy menstrual bleeding, dysmenorrhea, chronic pelvic pain, dyspareunia, abnormal uterine bleeding, infertility, uterus enlargement; approximately one third of patients are however asymptomatic [1, 4–6].

MRI findings of adenomyosis are:

- diffuse or focal enlargement of the uterus;

- thickening of JZ ≥12mm (focal or diffuse) representing the smooth muscle
hyperplasia accompanying the endometrial heterotopia;

- abnormal myometrial signal intensity: hyperintense foci on T1w images consistent with hemorrhage; abnormal low-signal intensity within the myometrium on T2-weighted images, representing foci of heterotopic endometrial tissue; cystic dilatation of heterotopic glands; cystic lesion showing hemorrhage in varying stages of organization, appearing hypointense on T2w images (adenomyoma); hyperintense linear striations radiating from the endometrium into the myometrium on T2w images, corresponding to invasion of the basal endometrium into the myometrium;

- lack of contour abnormality or mass effect;

- ill-defined margins between normal and abnormal myometrium;

- elliptic shape of a low- signal-intensity myometrial abnormality [4–9].

MRI appearance of adenomyosis depends on menstrual cycle phase [4], but objective criteria can be considered for diagnosis : JT ≥12 mm, JZ max/total myometrium ratio ≥40%, difference between the maximum and the minimum thickness of the JZ ≥5mm, the last parameter being independent from hormonal status [8]. Hemorrhagic foci can be emphasized with T2*w sequence [4]; high ADC coefficient is useful for differentiating adenomyosis from a malignancy, whereas cine-MRI can be to rule out transient myometrial contraction[5].

Differential Diagnosis List

Final Diagnosis

Adenomyosis

URL:	https://www.eurorad.org/case/14327
DOI:	10.1594/EURORAD/CASE.14327
ISSN:	1563-4086