MRI and Endometriosis: What Can an MRI Show?

What is endometriosis?

Endometriosis is a condition in which tissue similar to the lining of the uterus is found elsewhere in the body, most commonly within the pelvis.

It can be associated with symptoms including:

• —painful periods
• —persistent pelvic pain
• —pain during or after sex
• —painful bowel movements
• —urinary symptoms
• —fertility difficulties
• —fatigue
• —cyclical bowel or bladder symptoms.

Symptoms vary widely, and the severity of someone's symptoms does not always correspond to the amount of disease visible on imaging.

Where does imaging fit in?

In the UK, NICE recommends transvaginal ultrasound for people with suspected endometriosis, including when pelvic examination is normal.^[1]

Specialist ultrasound or pelvic MRI may then be used to assess deep endometriosis and map its extent.^[1]

MRI is particularly valuable when:

• —deep pelvic endometriosis is suspected
• —ultrasound findings are uncertain
• —disease mapping is needed before surgery
• —the anatomy is complex
• —symptoms persist despite previous treatment
• —disease outside the immediately accessible ultrasound field is a concern.

Recent European Society of Urogenital Radiology consensus guidance also supports MRI when specialist ultrasound is inconclusive or negative in a symptomatic patient, for pre-operative assessment, and in selected people with persistent symptoms after treatment.^[2]

What can MRI show?

Ovarian endometriomas

Endometriomas are ovarian cysts associated with endometriosis.

Blood products within an endometrioma produce characteristic appearances on MRI, particularly on T1- and T2-weighted sequences.

MRI can help assess:

• —which ovary is involved
• —whether both ovaries are involved
• —the number and size of endometriomas
• —the relationship between the ovaries and surrounding structures
• —other associated endometriosis.

Deep endometriosis

Deep endometriosis can involve structures including:

• —uterosacral ligaments
• —posterior vaginal wall
• —rectovaginal region
• —rectum and sigmoid colon
• —bladder
• —ureters
• —pelvic sidewalls and parametria.

Deep disease often contains fibrous tissue, so parts of it may appear relatively dark on T2-weighted MRI sequences.

Modern MRI reporting increasingly uses a compartment-based approach so the radiologist systematically assesses different areas of the pelvis.^[2,3]

Bowel endometriosis

MRI may demonstrate nodules involving the rectum or sigmoid colon and can help assess their:

• —location
• —size
• —longitudinal extent
• —relationship to surrounding structures.

This information can be particularly important when planning surgery.

Bladder and urinary-tract disease

Deep endometriosis may involve the bladder or ureters.

MRI protocols for suspected deep disease should therefore assess not only the pelvis but also look for consequences such as urinary-tract obstruction where appropriate.^[3]

What does an endometriosis MRI involve?

A pelvic MRI for endometriosis usually includes several different imaging sequences.

Contemporary ESUR recommendations support a structured protocol including multiplanar T2-weighted imaging, T1-weighted imaging and assessment extending sufficiently to evaluate relevant urinary anatomy.^[3]

Preparation varies between centres.

Depending on the department, instructions may include:

• —fasting for a period beforehand
• —arriving with a moderately full bladder
• —medication to temporarily reduce bowel movement
• —bowel preparation in some centres.

Do I need MRI contrast?

Intravenous contrast is not required for every endometriosis MRI.

The decision depends on the clinical circumstances, local protocol and whether there is a specific finding that requires further characterisation.

Your radiology department will decide whether contrast is appropriate for your examination.

Can MRI diagnose all endometriosis?

No.

This is one of the most important things to understand.

Imaging performs particularly well for ovarian endometriomas and many forms of deep endometriosis, especially when performed and interpreted by people with appropriate expertise.^[2,3,4]

However, superficial peritoneal endometriosis can be difficult or impossible to identify reliably on imaging.

This means:

Current NICE guidance explicitly states that diagnostic laparoscopy can still be considered when endometriosis is suspected despite normal ultrasound or MRI.^[1]

This is why imaging should always be interpreted alongside:

• —symptoms
• —examination findings where relevant
• —previous treatment
• —specialist clinical assessment.

Does a normal MRI mean my symptoms are not real?

Absolutely not.

A normal MRI means that the radiologist has not identified endometriosis that can be confidently demonstrated on that examination.

It does not mean:

• —you do not have pain
• —your symptoms are insignificant
• —nothing is wrong
• —superficial endometriosis has been excluded.

If symptoms remain suggestive of endometriosis, discuss the next step with your GP or gynaecology team.

Does specialist interpretation matter?

Yes.

NICE specifically recommends that specialist pelvic ultrasound and MRI for suspected deep endometriosis should be planned and interpreted by healthcare professionals with specialist expertise in gynaecological imaging.^[1]

This is because identifying and accurately mapping deep endometriosis can be technically demanding.

What happens if MRI does show deep endometriosis?

The next step depends on:

• —your symptoms
• —which structures are involved
• —fertility considerations
• —previous treatment
• —whether medical or surgical management is being considered.

Imaging can help your specialist team understand the extent of disease and plan management.

In complex deep endometriosis, this may involve a multidisciplinary team.

Questions you may want to ask after your MRI

• —Did the scan show an endometrioma?
• —Was there evidence of deep endometriosis?
• —Were the bowel, bladder or ureters involved?
• —Was adenomyosis seen?
• —Was the scan interpreted by someone experienced in endometriosis imaging?
• —If the MRI was normal but my symptoms persist, what happens next?

Where can I get further help?

Trusted UK resources include:

• —NHS
• —NICE — Endometriosis: diagnosis and management (NG73)
• —Endometriosis UK
• —specialist NHS endometriosis services.