Adenomyosis

Adenomyosis is a 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 dysmenorrhoea. Ultrasound and MRI are imaging modalities that may show characteristic findings.

Epidemiology

Classically, it has been taught that adenomyosis most commonly affects multiparous women of reproductive age. However, this was based on the results of pathologic examinations of hysterectomy specimens with studies therefore biasedbiassed towards patients who had surgery. Similarly, this may be the reason adenomyosis is seen with higher frequency in women with a history of uterine surgical procedures (e.g. Caesarean section, dilatation and curettage). Patients with high estrogenoestrogen exposure (e.g. short menstrual cycles, early menarche) have an increased risk of adenomyosis. It has a reported incidence that ranges widely from 5-70% (mean 20-30%), depending on the histological definition or the imaging modality used ¹².

Clinical presentation

Most patients with adenomyosis are asymptomatic. Symptoms related to adenomyosis include dysmenorrhoea, menorrhagia, dyspareunia, chronic pelvic pain, and menometrorrhagia ¹¹. The ectopic endometrial glands within the myometrium do not respond to cyclic ovarian hormones, unlike those of endometriosis. Pelvic tenderness on examination is associated with diffuse enlargement of the uterus.

Pathology

Adenomyosis is histologically-defined by the presence of ectopic endometrial tissue within the myometrium. The exact cause of adenomyosis is unknown, but it is thought that endometrial glands directly invade the myometrium, resulting in spiral vessel angiogenesis, adjacent smooth muscle hyperplasia and hypertrophy. 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.

Other hypotheses include invagination of the endometrium through the basalis alongside the intramyometrial lymphatics and embryologically displaced pluripotent mullerian remnants.

Associations

• co-existent endometriosis reported in 20% of cases ¹.
• leiomyomas: may be present in almost 50% of cases involving adenomyosis of the uterus ¹⁴
• other reported associations include
  • endometrial hyperplasia ¹⁴
  • endometrial polyps ¹⁴

Radiographic features

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.

Ultrasound

Pelvic ultrasound is usually the first and often the only imaging modality employed to investigate menorrhagia and dysmenorrhoea. Unfortunately, the sonographic features of adenomyosis are variable and may be absent. The reported sensitivity and specificity of transabdominal ultrasound are 32-63% and 95-97% respectively ⁷. However, it has been reported that transvaginal ultrasound is as sensitive (89%) and specific (89%) as MRI in diagnosing adenomyosis.

It may be useful to categorise ultrasound findings into three groups that mirror the histological findings ^15-17:

• "adeno": ectopic endometrial glands
  • subendometrial echogenic linear striations and/or nodules (specific sign) which extend from the endometrium and into the inner myometrium
  • hyperechoic islands and an irregular endometrial–myometrial junction ¹⁹
  • tiny (1-5 mm) anechoic myometrial and subendometrial cysts (specific sign): reflecting glands filled with fluid
  • cystic striations
• "myosis": muscular hyperplasia +/- hypertrophy, which may be hypoechoic
  • focal or diffuse myometrial bulkiness which may be asymmetric, typically of the fundal region and posterior wall ⁵
  • focal areas have relatively indistinct borders compared with those of leiomyomas
  • asymmetrical myometrial thickening
  • thickening of the transition zone can sometimes be visualised as a hypoechoic halo surrounding the endometrial layer of ≥12 mm thickness (less specific)
• vascularity: on colour Doppler
  • generally increased
  • areas of increased vascularity reciprocate distribution of lesions
  • pattern is of an increased number of tortuous vessels that penetrate myometrium

A "Venetian blind" appearance may(linear striations, parallel shadowing) may be seen as a combination of the aforementioned features: heterogeneous ^1,2, coarsened echotexture of the myometrium, and acoustic shadowing where endometrial tissues cause a hyperplastic reaction. The combination of this heterogeneity and the subendometrial echogenic nodular and linear striations is not dissimilar to the appearance of chronic liver parenchymal disease - hence, “cirrhosis of the uterus.”

When an adenomyoma is present, 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 the presence of calcifications strongly favours the latter ⁵.

MRI

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 thickness is up to ~5 mm) ⁵.

• T1
  • foci of high T1 signal are often seen, indicating menstrual haemorrhage into the ectopic endometrial tissues ⁷
• 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 areas of cystic change
  • the region may also have a striated appearance ⁵
• T1 C+ (Gd)
  • contrast-enhanced MRI 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.

History and etymology

It was first described by Rokitansky in 1860 as “cystosarcoma adenoides uterinum” and was later defined by Von Recklinghausen in 1896 ¹¹. 

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
  • on colour Doppler: tend to displace vessels, demonstrating circumferential peripheral flow
• uterine contractions
  • transient in nature
• vascular malformations
  • does not disrupt the endometrial-myometrial interface
  • on colour Doppler: demonstrates turbulent high-velocity flow
• malignancy
  • endometrial carcinoma
  • endometrial stromal sarcoma (ESS)
  • uterine tumour (e.g. uterine leiomyosarcoma)
  • myometrial metastases

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).