What is the recommended approach to diagnose endometriosis?

Diagnosing Endometriosis

The gold standard for diagnosing endometriosis is laparoscopy with histologic inspection, but transvaginal ultrasound (TVUS) should be used as the first-line imaging modality, followed by MRI if findings are indeterminate or negative with high clinical suspicion. 1, 2

Clinical Evaluation

• Assess for classic symptoms:
  • Cyclic pelvic pain
  • Dysmenorrhea (painful periods)
  • Dyspareunia (painful intercourse)
  • Infertility (present in 20-30% of cases)
  • Dyschezia (painful bowel movements)

Diagnostic Algorithm

Step 1: Initial Imaging

• Transvaginal ultrasound (TVUS) is the recommended first-line imaging modality 1, 2
  • Look for:
    • Ovarian endometriomas (homogenous low-level internal echoes)
    • Echogenic foci in the wall (hemosiderin deposits)
    • Multilocularity
    • Deep infiltrating endometriosis (DIE)
    • Uterosacral ligament involvement
    • Rectosigmoid involvement
  • Combined transabdominal and transvaginal US may provide more comprehensive assessment

Step 2: If TVUS is positive and adequate for surgical planning

• Proceed to treatment planning
• Preoperative imaging is associated with decreased morbidity and mortality and reduces the need for repeat surgeries 1

Step 3: If TVUS is negative but clinical suspicion remains high

• MRI pelvis without and with IV contrast 1, 2
  • Superior for detecting:
    • Deep infiltrating endometriosis
    • Adhesions
    • Bowel involvement
    • Urinary tract involvement
    • Lesions beyond the field of view of TVUS

Step 4: Definitive Diagnosis

• Laparoscopy with histologic inspection remains the gold standard 1, 3
  • Indicated when:
    • Imaging is inconclusive but symptoms persist
    • Surgical treatment is being considered
    • Other causes of symptoms have been ruled out

Special Imaging Considerations

Expanded Protocol TVUS

• Performed by specialists trained in endometriosis imaging
• Includes detailed evaluation of:
  • Uterosacral ligaments
  • Anterior rectosigmoid wall
  • Appendix
  • Diaphragm
  • Dynamic sliding maneuvers to evaluate organ mobility 1
• Requires bowel preparation or enema for detection of bowel lesions
• Requires specialized training (learning curve of at least 40 examinations) 1
• Has significantly higher sensitivity than routine pelvic US 1

MRI Protocol for Endometriosis

• Moderate bladder distention and vaginal contrast recommended
• T2-weighted imaging is most useful for detecting endometriotic lesions
• IV contrast helps differentiate endometriomas from ovarian malignancies 2
• Provides wider field of view than TVUS
• Useful for detecting urinary tract endometriosis and bowel involvement beyond the pelvis 2

Transrectal Ultrasound

• Useful for detecting deep infiltrating endometriosis
• High sensitivity (97%) and specificity (96%) for rectovaginal endometriosis
• Good for uterosacral ligament implants (80% sensitivity, 97% specificity) 1
• Limited to a small anatomic area but valuable in patients unable to undergo TVUS 1

Important Caveats

1. Operator Dependence: TVUS effectiveness is highly dependent on operator expertise. "Community US" is less beneficial than specialized protocols performed by trained operators 2

2. Negative Imaging: A negative scan cannot completely exclude endometriosis, particularly superficial peritoneal disease 2, 4

3. CT Limitations: CT is not recommended as an initial imaging modality for endometriosis diagnosis 1

4. Diagnostic Delay: Despite advances in imaging, diagnostic delay of 6-8 years is common 4

5. Classification Systems: The World Endometriosis Society recommends using a toolbox for surgical classification that includes the r-ASRM system and, where appropriate, the Enzian and EFI staging systems 1

By following this diagnostic algorithm and understanding the strengths and limitations of each imaging modality, clinicians can significantly reduce the diagnostic delay and improve outcomes for patients with endometriosis.