What are the diagnostic criteria for endometriosis?

Diagnostic Criteria for Endometriosis

Clinical Diagnosis Without Surgery

Endometriosis is fundamentally a clinical diagnosis that does not require surgical confirmation before initiating empiric treatment, with diagnosis based on characteristic symptoms, physical examination findings, and imaging confirmation of deep or ovarian disease. 1

Key Clinical Features That Establish Diagnosis

• Pain patterns including dysmenorrhea, dyspareunia (painful intercourse), dyschezia (painful defecation), dysuria (painful urination), or chronic pelvic pain are diagnostic features of endometriosis 1
• Infertility is present in approximately 50% of patients with endometriosis and should raise clinical suspicion 1
• Physical examination findings such as nodularity, fixed retroverted uterus, or tender uterosacral ligaments support the clinical diagnosis 1

Imaging-Based Diagnostic Criteria

First-Line Imaging Approach

• Transvaginal ultrasound (TVUS) is the recommended initial imaging modality, with sensitivity of 82.5% and specificity of 84.6% for endometriosis 1
• Expanded protocol TVUS (when performed by experts) demonstrates excellent performance for deep endometriosis detection and is comparable to MRI 1, 2
• Expanded protocol TVUS requires evaluation of uterosacral ligaments, assessment of anterior rectosigmoid wall, dynamic sliding maneuvers, bowel preparation or enema, and evaluation of appendix and diaphragm 1, 2

Specific Imaging Diagnostic Features

For Ovarian Endometriomas:

• Adnexal or ovarian masses with homogenous low-level internal echoes on ultrasound 2
• Echogenic foci in the wall or multilocularity increases diagnostic likelihood 2
• MRI shows 82-90% sensitivity and 91-98% specificity for endometriomas 2

For Deep Infiltrating Endometriosis:

• MRI demonstrates 92.4% sensitivity and 94.6% specificity for intestinal endometriosis 1
• MRI shows 88% sensitivity and 83.3% specificity for deep infiltrating endometriosis overall 1
• MRI diagnostic features include T2 dark spot sign, deep infiltrating lesions, and adhesions/cul-de-sac obliteration 1
• Transrectal ultrasound shows 97% sensitivity and 96% specificity for rectovaginal endometriosis 2

MRI Protocol Specifications

• MRI without IV contrast is sufficient for detecting deep endometriosis 1
• MRI with IV contrast is highly recommended to differentiate endometriomas from ovarian malignancies 1
• Moderate bladder distention and vaginal contrast improve lesion conspicuity 1, 2

Surgical Diagnostic Criteria (When Performed)

• Laparoscopy with histologic confirmation remains the gold standard for definitive diagnosis when surgery is performed, allowing visualization of endometriotic lesions 2
• However, laparoscopy is no longer required before initiating empiric treatment and is reserved for definitive treatment rather than diagnosis 1
• Histologic examination should confirm the presence of endometrial lesions, especially those with non-classical appearance 2
• Only experienced surgeons familiar with various appearances of endometriosis should rely on visual inspection alone 2

Surgical Classification Systems (When Surgery Performed)

• r-ASRM (revised American Society for Reproductive Medicine) classification should be completed for all patients undergoing surgery 2
• Enzian classification should be used for patients with deep endometriosis 2
• EFI (Endometriosis Fertility Index) should be documented for patients with fertility concerns 2

Biomarker Limitations

• CA-125 has no clinical utility for diagnosis and should not be used as a diagnostic tool 1
• CA-125 may be helpful only for monitoring clinical response in patients with confirmed extrauterine disease, but can be falsely elevated due to peritoneal inflammation or infection 1

Critical Diagnostic Algorithm

Step 1: Identify characteristic pain patterns (dysmenorrhea, dyspareunia, dyschezia, dysuria) and/or infertility 1

Step 2: Perform physical examination looking for nodularity, fixed retroverted uterus, or tender uterosacral ligaments 1

Step 3: Order transvaginal ultrasound as initial imaging, or expanded protocol TVUS if available with expert sonographer 1, 2

Step 4: If TVUS is inconclusive or deep infiltrating disease is suspected, proceed to MRI pelvis (with or without IV contrast depending on need to exclude malignancy) 1, 3

Step 5: Initiate empiric treatment based on clinical and imaging diagnosis without requiring surgical confirmation 1

Step 6: Reserve laparoscopy for definitive treatment planning or when diagnosis remains uncertain after imaging 1, 2

Critical Pitfalls to Avoid

• Do not rely on standard TVUS alone for deep endometriosis—expanded protocols or MRI are needed 1
• Do not use CT pelvis as initial imaging—it has no role in standard endometriosis diagnosis 1, 2
• Do not assume negative imaging excludes endometriosis—superficial peritoneal disease is poorly detected by all imaging modalities 1
• Do not delay treatment waiting for surgical confirmation—clinical diagnosis with imaging is sufficient to begin empiric therapy 1
• Do not use CA-125 for diagnostic purposes 1
• Standard TVUS has significant limitations, and expanded protocol TVUS requires special training with at least 40 examinations to develop proficiency 2