Adenomyosis of the uterus

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

Epidemiology

Adenomyosis typically affects women of reproductive age. In general, affected women are multiparous, and is 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 endometriosis¹.

Radiographic features

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

1. diffuse adenomyosis : most common
2. focal adenomyosis / adenomyoma : some consider these as separate (see below)
3. cystic adenomyosis / 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 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 echotexture) ^1-2
  • hyper-echoic : islands of endometrial glands
  • hypo-echoic :  associated muscle hypertrophy
  • can give a "venetian blind" appearance
• small myometrial - sub endometrial cysts

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. 
• 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

• normal uterus
• diffuse uterine leiomyomatosis
• myometrial contraction : transient finding
• malignancy
  • endometrial carcinoma
  • endometrial stromal sarcoma (ESS)

For focal disease (adenomyoma) consider

• uterine fibroma (leiomyoma)
  • better defined than adenomyoma
  • may have pseudocapsule of compressed adjacent myometrial tissue ⁵
• malignancy
  • endometrial carcinoma
  • endometrial stromal sarcoma (ESS)
  • uterine tumour (e.g. uterine leiomyosarcoma)

Whether focal or diffuse, another potential differential is treatment of breast cancer with Tamoxifen which can lead to poorly defined endometrial hyperplasia and endometerial polyps that can mimic adenomyosis ⁴ (see Tamoxifen associated endometrial changes).