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Adenomyosis of the uterus

Adenomyosis of the uterus is a relatively common condition and is thought by many to be on the spectrum of endometriosis.

Epidemiology

Adenomyosis typically affects women of reproductive age. In general, affected women are multiparous, and the condition seen with higher frequency in woman with a history of surgical uterine procedures (e.g. Caesarian section, dilatation and curettage). It has a reported incidence ranging widely from 5 to 70% 11.

Clinical presentation

Most patients with adenomyosis have symptoms and typically present with menorrhagia and dysmenorrhea. The ectopic endometrial glands within adenomyosis generally do not respond to cyclic ovarian hormones, unlike those of endometriosis.

Pathology

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.

Associations

In 20% of cases is associated with co-existent endometriosis 1.

Radiographic features

Imaging features are variable and in many instances very subtle. Three (some say four) forms can be distinguished:

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 it may also 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

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 bulkiness, typically of the posterior wall 5
  • heterogeneous echogenicity (heterogenous myometrial echotexture1-2
    • 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
  • small myometrial: sub endometrial cysts
  • thickening of the transition zone sometimes  can be visualized as a hypoechoic halo surrounding the endometrial layer of 12 mm or more thickness
  • subendometrial echogenic linear striations
  • subendometrial echogenic nodules

When an adenomyoma is present, then appearances may closely mimic those of a uterine fibroid, which may also co-exist.

Hysterosalpingogram (HSG)

May show diverticula extending into the myometrium 3.

CT

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 presence of calcifications strongly favours the latter 5.

Pelvic MRI

MRI is the modality of choice to diagnose and characterise adenomyosis, and T2 weighted images (sagittal and axial) are most useful. It has a very diagnostic accuracy with 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 no more than 5 mm) 5.

  • T2
    • 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
  • T1
    • 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 in adenomyosis, however if performed, it shows enhancement of the ectopic endometrial glands

Treatment and prognosis

The treatment depends on 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.

Differential diagnosis

The differential depends on the macroscopic distribution of endometrial tissue.

For diffuse disease consider

For focal disease (adenomyoma) consider

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).

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