Uterine fibroid embolization is used as an alternative to hysterectomy in selected patients and MRI is a key investigation in allowing not only pre-procedure assessment but also assessing post-procedure outcome.
MR imaging is used to 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.
- 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 butyl bromide 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 features do not represent other pathology.
MR appearances of uterine fibroids is variable, and depends on whether the fibroids are:
- hyaline or cystic
Non-degenerate fibroids shows appear as well-circumscribed masses of homogenous decreased signal intensity (compared to outer myometrium) on T2 weighted images. Cellular leiomyomas show a slightly higher signal intensity on T2 weighted images as well as enhancement on post-contrast images.
Degenerate fibroids show variable appearances on T2 weighted images and contrast-enhanced images.
Fibroids with cystic degeneration show high signal intensity on T2 weighted images. Cystic areas do not show enhancement.
Fibroids with hyaline or calcific degeneration show low signal intensity on T2 weighted images, this is similar to a typical fibroid3. Fibroids with hyaline degeneration may show cobblestone appearance on post contrast images1.
Fibroids with myxoid degeneration demonstrate very high signal intensity on T2 weighted images and minimal enhancement on contrast-enhanced images4.
Fibroids with red degeneration may show peripheral or diffuse high signal intensity on T1 weighted images (probably due to the proteinaceous content of blood or T1 shortening effects of methaemoglobin). They may show variable signal intensity on T2 weighted images, with or without a low signal intensity rim.
Uterine fibroids are, usually, seen within the uterine corpus, approximately 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 and are defined by the presence of a stalk which is less than 50% of the fibroid diameter.
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 occur1.
Enhancement of the fibroids depends on their vascularity which is assessed on post-contrast images. The goal of 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 allows assessment of the anatomy of the uterine vessels. It also has a role in depicting ovarian artery contribution to the uterine fibroid blood supply.
MRI helps in confirming the diagnosis of uterine fibroids and differentiating it from a variety of conditions gynaecological conditions.
Post UAE MR appearances
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.
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 weighted images.
Successful embolization may result in some reduction of fibroid size.
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.
This is considered a late treatment failure.
Complications depicted on MRI
- 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 imply infection)
- 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 weighted images and areas of high signal intensity on T2 weighted images
- 1. Kirby JM, Burrows D, Haider E et-al. Utility of MRI before and after uterine fibroid embolization: why to do it and what to look for. Cardiovasc Intervent Radiol. 2011;34 (4): 705-16. doi:10.1007/s00270-010-0029-2 - Pubmed citation
- 2. Verma SK, Gonsalves CF, Baltarowich OH et-al. Spectrum of imaging findings on MRI and CT after uterine artery embolization. Abdom Imaging. 2010;35 (1): 118-28. doi:10.1007/s00261-008-9483-6 - Pubmed citation
- 3. Murase E, Siegelman ES, Outwater EK et-al. Uterine leiomyomas: histopathologic features, MR imaging findings, differential diagnosis, and treatment. Radiographics. 19 (5): 1179-97. Radiographics (citation) - Pubmed citation
- 4. Deshmukh SP, Gonsalves CF, Guglielmo FF et-al. Role of MR imaging of uterine leiomyomas before and after embolization. Radiographics. 2012;32 (6): E251-81. Radiographics (full text) - doi:10.1148/rg.326125517 - Pubmed citation