Adenomyosis of the uterus
Adenomyosis of the uterus is a relatively common, benign uterine pathology. It is thought by many to be on the spectrum of endometriosis, with ectopic endometrial tissue in the myometrium. Adenomyosis may present with menorrhagia and dysmenorrhea. Ultrasound and MRI are imaging modalities that may show characteristic findings.
Adenomyosis typically affects women of reproductive age. In general, affected women are multiparous, and the condition is seen with higher frequency in a woman with a history of uterine surgical procedures (e.g. Caesarian section, dilatation and curettage). It has a reported incidence that ranges widely from 5 to 70%, depending on the histological definition used or the imaging modality used 12.
Most patients with adenomyosis are symptomatic and typically present with menorrhagia and dysmenorrhea. They may present with chronic pelvic pain. The ectopic endometrial glands within adenomyosis do not respond to cyclic ovarian hormones, unlike those of endometriosis.
Adenomyosis is histologically defined by the presence of ectopic endometrial tissue within the myometrium. Benign invasion of the myometrium by the endometrium also results in adjacent smooth muscle hyperplasia. It has been postulated that this dysfunctional hypertrophied muscular tissue surrounding the ectopic endometrial glands prevents uterine contractions from tamponading bleeding myometrial arterioles, hence, these patients frequently present with dysfunctional uterine bleeding or menorrhagia.
Co-existent endometriosis in 20% of cases 1.
Imaging features are variable and in many instances very subtle. Three (some say four) forms can be distinguished:
- diffuse adenomyosis: most common
- focal adenomyosis and adenomyoma: some consider these as separate (see below)
- cystic adenomyosis and adenomyotic cyst: rare
Adenomyosis is usually relatively generalised, affecting large portions of the uterus (typically the posterior wall), but sparing the cervix. Despite often marked enlargement of the uterus, the overall contour is usually preserved 5.
In some cases, adenomyosis may be localised, forming a mass. In such cases, the term adenomyoma may be used, although there appears to be some disagreement about whether the terms focal adenomyosis and adenomyoma refer to exactly the same entity (please refer to the article on adenomyoma for further discussion).
A rare variant is cystic adenomyosis which is believed to be the result of repeated focal haemorrhages resulting in cystic spaces filled with altered blood products 5.
Pelvic ultrasound is usually the first and often the only imaging modality employed to investigate menorrhagia and dysmenorrhea. Unfortunately, the sonographic features of adenomyosis are variable and may be absent. The reported sensitivity and specificity of trans-abdominal ultrasound are 32-63% and 95-97% respectively 7.
The spectrum of findings includes:
- normal-appearing uterus
- focal or diffuse myometrial bulkiness, typically of the posterior wall 5
- thickening of the transition zone can sometimes be visualised as a hypoechoic halo surrounding the endometrial layer of ≥12 mm thickness
- subendometrial echogenic linear striations
- subendometrial echogenic nodules (specific sign)
- small myometrial cysts / subendometrial cysts (specific sign)
- heterogeneous echogenicity (heterogenous myometrial echotexture) 1-2
- hyperechoic: islands of endometrial glands
- hypoechoic: associated muscle hypertrophy
- a "Venetian blind" appearance may be seen due to subendometrial echogenic linear striations and acoustic shadowing where endometrial tissues cause a hyperplastic reaction
May show diverticula extending into the myometrium 3.
CT is unable to diagnose adenomyosis but may suggest its presence when uterine enlargement is present. Distinguishing between adenomyosis and uterine fibroids on CT is difficult if not impossible, although the presence of calcifications strongly favours the latter 5.
Pelvic MRI is the modality of choice to diagnose and characterise adenomyosis, and T2 weighted images (sagittal and axial) are most useful. MRI has a sensitivity of 78-88% and a specificity of 67-93% 7.
The most easily recognised feature is thickening of the junctional zone of the uterus to more than 12 mm, either diffusely or focally (normal junctional zone measures up to ~5 mm) 5.
- typically a region of adenomyosis appears as an ill-defined ovoid/diffuse region of thickening, often with small high T2 signal regions representing small regions of cystic change
- the region may also have a striated appearance 5
- foci of high T1 signal are often seen, indicating menstrual haemorrhage into the ectopic endometrial tissues 7
T1 C+ (Gd)
- contrast enhanced MR evaluation is usually not indicated for evaluation of adenomyosis, however, if performed, it shows enhancement of the ectopic endometrial glands
Treatment and prognosis
Treatment depends on the severity of symptoms and the need to preserve fertility. In some instances, suppression of normal cyclical hormone-induced proliferation of endometrial tissue (e.g. GnRH agonist) is sufficient.
In women with severe symptoms not relieved medically, and in whom fertility is no longer desirable, a hysterectomy may be performed.
The differential depends on the macroscopic distribution of endometrial tissue.
For diffuse disease consider:
- normal uterus
- diffuse uterine leiomyomatosis
- myometrial contraction: transient finding
For focal disease (adenomyoma) consider:
uterine fibroma (leiomyoma)
- better defined than adenomyoma
- may have pseudocapsule of compressed adjacent myometrial tissue 5
Whether focal or diffuse, another potential differential is treatment of breast cancer with Tamoxifen which can lead to poorly defined endometrial hyperplasia and endometrial polyps that can mimic adenomyosis 4 (see: Tamoxifen associated endometrial changes).
Ultrasound - gynaecology
- ultrasound (introduction)
- acute pelvic pain
- chronic pelvic pain
- Mullerian duct anomalies
- ovarian follicle
- ovarian torsion
- pelvic inflammatory disease
- ovarian cysts and masses
- ovarian cyst
- corpus luteum
- haemorrhagic ovarian cyst
- ruptured ovarian cyst
- ovarian epithelial tumours
- granulosa cell tumours of the ovary
- paraovarian cyst
- polycystic ovaries
- ovarian hyperstimulation syndrome
- post-hysterectomy ovary
- fallopian tube
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