Uterine artery embolisation: MRI assessment

Uterine artery embolisation (UAE) is used as an alternative to hysterectomy in selected patients and MRI assessment is key in allowing not only pre-procedure assessment but also assessing post-procedural outcome.  

For a general discussion of the underlying condition refer to the article on uterine fibroids. For discussion of the indications and technique, refer to the article on uterine artery embolisation

MRI features

MRI is used for patient selection, planning and documenting baseline appearances prior to uterine artery embolisation (UAE). Additionally MRI is also useful following UAE, where it is used to assess post-embolisation outcome and complications. 

MR technique
  • T1 and T2 fast spin echo (FSE) in sagittal, coronal and axial planes
  • MR angiography using 3D gradient recalled echo with IV gadolinium (e.g. 20 ml gadodiamide)
  • 20 mg IV hyoscine butylbromide is given to suppress uterine and intestinal peristalsis
Pre-embolisation assessment

Pre-embolisation imaging should assess appearance, location, size, and vascularity as well as ensure that uterine findings do not represent other pathology.  

Appearance

MRI appearances of uterine fibroids are variable, and depends on whether the fibroids are: 

  1. non-degenerate
  2. degenerate:
    • hyaline or cystic 
    • myxoid
    • red

Non-degenerate fibroids appear as well-circumscribed masses of homogenous decreased signal intensity (cf. outer myometrium) on T2 images. Cellular leiomyomas show a slightly higher signal intensity on T2 images as well as enhancement on post-contrast images.

Degenerate fibroids show variable appearances on T2 images and contrast-enhanced images.

Fibroids with cystic degeneration show high signal intensity on T2 images. Cystic areas do not show enhancement.

Fibroids with hyaline or calcific degeneration show low signal intensity on T2 images, this is similar to a typical fibroid 3. Fibroids with hyaline degeneration may show a cobblestone appearance on post-contrast images 1

Fibroids with myxoid degeneration demonstrate very high signal intensity on T2 images and minimal enhancement on contrast-enhanced images 4.

Fibroids with red degeneration may show peripheral or diffuse high signal intensity on T1 images (probably due to the proteinaceous content of blood or T1 shortening effects of methaemoglobin). They may show variable signal intensity on T2 images, with or without a low signal intensity rim.

Location

Uterine fibroids are, usually, seen within the uterine corpus, ~8% occur within the cervix.

They may be classified as follows:

  • submucosal: projecting within the endometrial cavity
  • intramural: within the substance of the myometrium
  • subserosal: lie beneath the serosa

Pedunculated fibroid: can be subserosal or submucosal in location, this is defined by the presence of a stalk which <50% of the fibroid diameter.

Fibroid size

Although the relationship between the size of the fibroid and post-embolisation outcome is not entirely clear, most operators select a threshold of 13-15 cm. It is suspected that embolisation of larger leiomyomas may still result in bulk symptoms due to residual fibroid mass. Additionally, with larger amount of necrotic tissue, prolonged post-embolisation syndrome might occur 1.

Vascularity

Enhancement of the fibroids depends on their vascularity which is assessed on post-contrast images. The goal of uterine artery embolisation (UAE) is to cause infarction of the fibroid while maintaining endometrial and myometrial perfusion. Fibroids that are already infarcted are unlikely to show volume reduction following UAE.

Vascular anatomy is assessed on 3D contrast-enhanced MRA. This permits assessment of the anatomy of the uterine vessels. It also has a role in depicting ovarian artery contribution to the uterine fibroid blood supply. 

Differential diagnosis

MRI helps in confirming the diagnosis of uterine fibroids and differentiating it from a variety of gynaecological conditions. 

Post UAE MRI appearances
Vascularity

Lack of enhancement on post-contrast images in a previously enhancing fibroid represents fibroid infarction. Complete fibroid infarction has been shown to have a higher symptom control and a lower rate of gynaecological intervention at 5 years when compared to incomplete infarction.

Persistent fibroid enhancement on post-contrast images or visualisation of the uterine arteries on MRA is considered treatment failure.

Liquefaction

With increased interval between 3 months and 1 year following embolisation, there is progressive liquefaction of necrotic fibroids. This results in increased signal intensity on T2 images.

Size reduction

Successful embolisation may result in some reduction of fibroid size.

Location

Some fibroids (1-5%)  may demonstrate change in location, e.g. a submucosal fibroid may become endocavitary. Similarly subserosal fibroids may develop a submucosal or intramural component.

Fibroid recurrence

This is considered a late treatment failure.

Complications depicted on MRI

Endometritis

  • uterine enlargement
  • T1 hyperintense intracavitatory haematoma
  • gas associated with endometritis appears as a signal void on all sequences (the presence of gas alone does not indicate infection)

Uterine infarction

  • uterine infarction is a very rare complication
  • non-enhancement of uterine corpus
  • widening of the endometrial stripe
  • the uterus shows homogeneous low signal intensity on T1 images and areas of high signal intensity on T2 images
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Article information

rID: 16285
Synonyms or Alternate Spellings:
  • Uterine arterial embolisation : MRI assessment
  • MRI assessment of uterine arterial embolisation
  • MRI assessment of uterine artery embolisation

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