MRI (Magnetic Resonance Imaging) is one of the imaging techniques used to detect endometriosis. While not always the first diagnostic tool, MRI can be highly useful in identifying specific types and locations of the disease, particularly when lesions are deep or involve the bowel, bladder, or other organs.
Endometriosis is a long-term condition where tissue resembling the lining of the uterus (the endometrial stroma and glands) grows in areas outside the womb. This tissue responds to hormonal changes and may cause pain, inflammation, and scar tissue (adhesions).
How Common Is Endometriosis?
Endometriosis affects an estimated 10% of women and people assigned female at birth (AFAB) during their reproductive years. This corresponds to approximately 190 million individuals globally [1].
Due to varied symptoms and limited detection by physical examination alone, imaging plays an important role in assessing the extent of disease and planning treatment.
Where Does Endometriosis Occur in the Body?
Endometrial-like tissue can grow in multiple areas, often affecting:
- Ovaries – often forming cysts called endometriomas
- Fallopian tubes
- Pelvic peritoneum (lining of the abdominal cavity)
- Uterosacral ligaments – connective tissue behind the uterus
- Bladder and ureters – the tubes connecting kidneys to the bladder
- Bowel and rectum
- Less commonly: diaphragm, lungs, or abdominal wall
These abnormal growths respond to hormonal changes and may cause inflammation and fibrosis (thickening or scarring of tissue).
What Symptoms Might Prompt an MRI?
MRI may be recommended if symptoms are severe, persistent, or do not improve with initial treatment. These may include:
- Intense pelvic pain or period pain
- Pain during intercourse
- Painful bowel movements or urination, especially during menstruation
- Chronic fatigue
- Suspected bowel or bladder involvement
- Signs of an ovarian cyst or endometrioma on ultrasound
MRI is particularly helpful when surgery is being considered or if deep infiltrating endometriosis (DIE) is suspected.
What Can an MRI Show in Endometriosis?
MRI uses magnetic fields and radio waves to produce detailed images of internal organs and soft tissues. It can reveal:
- Endometriomas (ovarian cysts filled with blood)
- Thickened ligaments or fibrous tissue
- Lesions within or near the bowel or bladder
- Nodules in the pelvic wall or between organs
- Distortion of pelvic anatomy due to adhesions
MRI is especially useful for mapping deep infiltrating endometriosis (DIE)—a severe form where lesions grow deep into tissues and organs.
Advantages of MRI for Diagnosing Endometriosis
- Non-invasive – no incisions or instruments inserted
- No radiation – unlike CT scans or X-rays
- Highly detailed – good for soft tissue contrast
- Pre-surgical planning – helps surgeons identify lesion location and depth
MRI is more effective when done with specific protocols tailored for endometriosis. This may include having the scan done at certain times in the menstrual cycle or using contrast agents to improve image clarity.
Limitations of MRI in Endometriosis
Despite its benefits, MRI has limitations:
- Cannot detect all types – especially superficial peritoneal lesions (small implants on the abdominal lining)
- Less sensitive than laparoscopy – small or scattered lesions may be missed
- Availability and cost – access may be limited or require specialist referral
- Operator dependency – accuracy depends on radiologist expertise and scan technique
MRI is usually not the first-line test. It is often used after transvaginal ultrasound (TVUS) or when planning laparoscopic surgery.
Comparing MRI to Other Imaging Methods
Transvaginal ultrasound (TVUS)
- First-line imaging method for pelvic pain
- Useful for detecting endometriomas and pelvic cysts
- Less sensitive for deep lesions or bowel involvement
MRI
- Better for deep infiltrating endometriosis
- More accurate for bowel, bladder, and rectovaginal lesions
- Non-invasive and detailed
Laparoscopy
- Gold standard for diagnosis
- Involves surgical insertion of a camera through the abdomen
- Allows for biopsy and treatment during the same procedure
Misconceptions About MRI and Endometriosis
Myth: MRI can diagnose all cases of endometriosis
Fact: MRI may miss small or superficial lesions. It is not a replacement for surgical confirmation in unclear cases.
Myth: If the MRI is normal, there is no endometriosis
Fact: Many individuals with negative imaging still have confirmed disease through laparoscopy.
Myth: MRI is always necessary to diagnose endometriosis
Fact: Diagnosis can be made based on clinical symptoms, history, and response to treatment, especially in mild cases.
When Should You Request an MRI?
An MRI may be appropriate if you:
- Have persistent pain that is not explained by ultrasound
- Suspect deep endometriosis involving bowel or bladder
- Are preparing for endometriosis surgery and need detailed mapping
- Have symptoms suggesting complex or widespread disease
Your GP or gynaecologist can refer you for MRI, ideally to a centre experienced in pelvic imaging.
Conclusion
MRI can be a valuable tool in identifying endometriosis, particularly in more severe or complex cases. While it cannot detect all forms of the disease, it offers detailed visualisation of deeper lesions and can support both diagnosis and surgical planning.
However, MRI is not a standalone test. It is best used alongside clinical evaluation, ultrasound, and—if necessary—laparoscopy. If your symptoms are persistent and affecting your quality of life, speak to a healthcare provider for a comprehensive assessment.
References
[1] Giudice, L.C. Endometriosis: Science and Practice
[2] Vercellini, P., et al. Clinical Management of Endometriosis
