Recommended Imaging Techniques for Diagnosing Endometriosis
Transvaginal ultrasound (TVUS) should be considered the first-line imaging modality for diagnosing endometriosis, with MRI reserved for cases with indeterminate findings or for surgical planning of complex cases. 1
Primary Imaging Options
First-Line Imaging:
- Transvaginal ultrasound (TVUS) - Excellent for detecting:
- Ovarian endometriomas (high sensitivity and specificity)
- Deep infiltrating endometriosis (DIE) when performed by trained operators
- Rectosigmoid involvement
- Uterosacral ligament involvement
Second-Line Imaging:
- MRI pelvis without and with IV contrast - For cases with:
- Indeterminate TVUS findings
- Need for comprehensive surgical planning
- Suspected complex or multifocal disease
Diagnostic Performance by Endometriosis Type
1. Ovarian Endometriomas
- TVUS: Excellent first-line modality 1, 2
- Typical appearance: adnexal/ovarian mass with homogenous low-level internal echoes
- Diagnostic features: echogenic foci in wall (hemosiderin deposits) and multilocularity 1
2. Deep Infiltrating Endometriosis (DIE)
3. Superficial Peritoneal Endometriosis
- Most challenging to diagnose with any imaging modality 2, 4
- MRI: Better than TVUS but still limited sensitivity 1
- Sonographic evaluation still in its infancy 4
Enhanced TVUS Techniques for Better Diagnosis
Key Maneuvers for TVUS:
- Uterine sliding sign: High diagnostic performance for pouch of Douglas obliteration 1
- Assessment of nodules at sites of tenderness 1
- Evaluation of ovarian mobility 1
- Identification of hypoechoic nodules outside ovaries 1
Transabdominal US as Adjunct to TVUS:
- Widens field of view beyond TVUS capabilities 1
- Useful for detecting:
- Urinary tract endometriosis
- Bowel involvement beyond pelvis (appendix, terminal ileum, cecum, sigmoid) 1
Role of MRI in Endometriosis Diagnosis
Indications for MRI:
- Indeterminate TVUS findings 1
- Surgical planning for complex cases 1
- Large field of view needed to assess entire urinary/gastrointestinal tracts 1
MRI Protocol Considerations:
- MRI without IV contrast: Adequate for diagnosis of DIE 1
- MRI with IV contrast: Recommended by Society of Abdominal Radiology for:
- Differentiating endometriomas from ovarian malignancies
- Diagnosing other pelvic conditions with similar symptoms 1
Important Caveats and Pitfalls
TVUS Limitations:
- Highly operator-dependent 1, 4
- "Community US" less beneficial than specialized protocols 1
- Negative scan cannot completely exclude endometriosis 4
- Limited sensitivity for superficial peritoneal disease 2, 4
CT Limitations:
- Not recommended as initial imaging modality for endometriosis 1, 5
- No relevant literature supporting CT for diagnosis of endometriosis 1
- May detect incidental findings of endometriosis when performed for other reasons 5
Training Considerations:
- TVUS accuracy significantly higher when performed by trained operators 1
- Study comparing trained vs. untrained operators showed TVUS predicted bowel endometriosis only when performed by trained operators 1
Algorithmic Approach to Endometriosis Imaging
Initial imaging: TVUS (transvaginal ± transabdominal) 1
- If positive and adequate for surgical planning → Proceed to treatment
- If negative but high clinical suspicion → Proceed to step 2
Secondary imaging: MRI pelvis without and with IV contrast 1
- Provides comprehensive assessment
- Better for detecting superficial peritoneal disease
- Excellent for surgical planning of complex cases
Special cases:
By following this evidence-based approach to imaging for endometriosis, clinicians can optimize diagnosis, reduce diagnostic delay, and improve surgical planning while minimizing unnecessary procedures.