What is the diagnostic approach to endometriosis?

Diagnostic Approach to Endometriosis

Laparoscopy with histologic confirmation remains the gold standard for definitively diagnosing endometriosis, as it allows direct visualization of lesions and histopathologic verification. 1

Initial Diagnostic Evaluation

• First-line diagnostic investigations for endometriosis include physical examination and pelvic ultrasound 2
• The physical examination should assess for:
  • Site-specific tenderness in the pelvis
  • Mobility and fixation of the uterus
  • Nodularity in the posterior fornix or uterosacral ligaments 3

Imaging Modalities

Transvaginal Ultrasound (TVUS)

• TVUS is the preferred initial imaging modality, especially when combined with real-time physical examination 4
• TVUS can effectively detect both ovarian and non-ovarian endometriosis 4
• Endometriomas typically appear as adnexal or ovarian masses with homogenous low-level internal echoes 4
• The presence of echogenic foci in the wall (hemosiderin deposits) or multilocularity increases likelihood of endometrioma diagnosis 4
• Dynamic ultrasound assessment should include:
  • Uterine sliding sign
  • Assessment for nodules at sites of tenderness
  • Evaluation of ovarian mobility
  • Identification of hypoechoic nodules outside the ovaries 4

Expanded Protocol TVUS

• Specialized expanded protocol TVUS performed by experts can identify and map deep endometriosis with higher sensitivity than routine ultrasound 4, 1
• This protocol includes:
  • Evaluation of uterosacral ligaments, anterior rectosigmoid wall, appendix, and diaphragm
  • Dynamic sliding maneuvers to assess organ mobility 4
  • Often performed after bowel preparation for better detection of bowel lesions 4
• Requires special training with a learning curve of at least 40 examinations 4, 1
• Currently not widely available in the United States 4

Magnetic Resonance Imaging (MRI)

• MRI is an excellent imaging modality for preoperative diagnosis of endometriosis 4
• MRI has 82-90% sensitivity and 91-98% specificity for diagnosing endometriomas 4
• Particularly useful when TVUS findings are indeterminate or when assessment for deep infiltrating endometriosis is required 4
• Typical MRI features of endometriomas:
  • High signal on T1-weighted with low signal on T2-weighted images (T2 shading) 4
  • T2 dark spot sign has 93% specificity in differentiating endometriomas from hemorrhagic cysts 4
• Deep infiltrating endometriosis appears as low signal intensity regions with or without hyperintense foci on T2 and/or T1-weighted images 4
• MRI can detect signs of adhesions:
  • Uterus fixed in retroversion
  • Low-signal intensity bands
  • Obliteration of organ interfaces
  • Obliteration of the cul-de-sac 4

Specialized MRI Protocols

• Expert consensus recommends tailored MRI protocols for detection of deep endometriosis 4
• Moderate bladder distention and vaginal contrast are recommended to improve lesion visibility 4

Transrectal Ultrasound

• Useful for detecting deep infiltrating endometriosis 4
• Shows high sensitivity (97%) and specificity (96%) for rectovaginal endometriosis 4
• Sensitivity of 80% and specificity of 97% for uterosacral ligament implants 4
• Limited to a small anatomic area but valuable in patients unable to undergo TVUS 4

Laboratory Testing

• Serum CA-125 has limited utility as a diagnostic marker, especially for minimal or mild disease 1
• Usually elevated only in advanced stages and therefore not suitable for routine screening 5

Definitive Diagnosis

• Laparoscopy with histologic confirmation remains the gold standard 1, 5
• The American Society for Reproductive Medicine recommends documentation using:
  • r-ASRM (revised American Society for Reproductive Medicine) classification for all patients
  • Enzian classification for patients with deep endometriosis
  • EFI (Endometriosis Fertility Index) for patients with fertility concerns 1
• Peritoneal biopsy should be used to diagnose questionable peritoneal lesions 1
• Only experienced surgeons familiar with various appearances of endometriosis should rely on visual inspection alone 1

Diagnostic Algorithm

1. Initial evaluation with history, physical examination, and transvaginal ultrasound 2
2. If findings are inconclusive or deep infiltrating endometriosis is suspected, proceed to:
   • Expanded protocol TVUS (if available with expert sonographer) 4
   • MRI pelvis 4
   • Transrectal ultrasound (especially for rectovaginal disease) 4
3. Definitive diagnosis via laparoscopy with histologic confirmation 1
4. In cases of multiorgan involvement or complex disease, a multidisciplinary team approach is recommended 2

Common Pitfalls and Caveats

• Diagnostic delay is common due to variable presentation and limitations of non-invasive testing 6
• The correlation between symptoms and stage of endometriosis is often poor 5
• Some forms of endometriosis, such as "subtle" or microscopic endometriosis, remain controversial regarding their clinical significance 1
• CT is not recommended for the initial imaging evaluation of suspected endometriosis 4
• Doppler assessment is important - endometrial implants have limited vascularity, and the presence of Doppler blood flow in a suspected implant should prompt investigation for neoplasm 4
• Malignant transformation of endometriosis occurs in approximately 0.7-1.6% of women with endometriosis 3