What is the approach to diagnosing endometriosis?

Diagnosing Endometriosis

Transvaginal ultrasound (TVUS) is the recommended initial imaging modality for suspected endometriosis, with expanded protocol TVUS plus transabdominal ultrasound or MRI pelvis (with or without IV contrast) being equally appropriate first-line options. 1, 2

Clinical Diagnosis Framework

The diagnosis of endometriosis is fundamentally clinical and does not require surgical confirmation before initiating empiric treatment. 3 However, imaging plays a critical role in treatment planning, reducing surgical morbidity, and preventing incomplete surgeries. 1

Key Clinical Features to Identify

• Pain patterns: Dysmenorrhea, dyspareunia, dyschezia, dysuria, or chronic pelvic pain 1
• Infertility: Present in approximately 50% of patients with endometriosis 1
• Physical examination findings: Though often nonspecific, may reveal nodularity, fixed retroverted uterus, or tender uterosacral ligaments 1

Imaging Algorithm

First-Line Imaging

Option 1: Transvaginal Ultrasound (Preferred Initial Approach)

• Standard TVUS has 82.5% sensitivity and 84.6% specificity for endometriosis 2
• Expanded protocol TVUS (when available) demonstrates excellent performance for deep endometriosis (DE) detection and is comparable to MRI 1
• Expanded protocols include evaluation of uterosacral ligaments, rectosigmoid wall, appendix, and dynamic sliding maneuvers 1
• Critical limitation: Expanded protocol TVUS requires specialized training (minimum 40 examinations learning curve) and is not widely available in the United States 1
• Add transabdominal ultrasound to widen field of view for urinary tract and bowel involvement beyond the pelvis 1

Option 2: MRI Pelvis (Equally Appropriate Initial Option)

• MRI without IV contrast is sufficient for detecting deep endometriosis 1
• MRI with IV contrast is highly recommended to differentiate endometriomas from ovarian malignancies (important given increased cancer risk) and to identify other pelvic pathology 1
• MRI has 78% sensitivity and 93% specificity for adenomyosis when ultrasound is equivocal 2
• Superior for surgical planning due to large field of view and automated acquisition 1
• Performance varies by location: excellent for deep endometriosis, poor for superficial peritoneal disease 1

When to Choose MRI Over Ultrasound

• TVUS inconclusive or technically limited 2
• Coexisting pathology (e.g., leiomyomas present—TVUS sensitivity drops to 33.3%) 2
• Deep infiltrating endometriosis suspected (bowel, bladder, ureter involvement) 3
• Obese patients where transabdominal views are limited 1
• Comprehensive surgical planning needed before complex resection 1, 4

Specialized Imaging for Specific Scenarios

Rectosigmoid Endometriosis Suspected:

• Expanded protocol TVUS or MRI pelvis are appropriate initial studies 1
• Standard CT pelvis is not appropriate for endometriosis evaluation 1
• Specialized techniques (CT with water enema, MR colonography) exist but are not widely available 1

Biomarkers

CA-125 has limited diagnostic utility but may help monitor treatment response in patients with extrauterine disease. 2 However, it can be falsely elevated due to peritoneal inflammation or infection, limiting its specificity. 2

Surgical Diagnosis

Laparoscopy with histologic confirmation remains the definitive diagnostic method but is no longer required before initiating treatment. 3, 5 Multiple gynecologic organizations now recommend empiric hormonal therapy without immediate surgical diagnosis. 3

Indications for Surgical Diagnosis:

• Empiric medical therapy fails 3
• Immediate definitive diagnosis required 3
• Patient desires pregnancy and surgical treatment is indicated 3
• Preoperative imaging shows complex disease requiring specialized surgical planning 1

Critical Pitfalls to Avoid

• Do not delay treatment waiting for surgical confirmation—empiric therapy is appropriate with clinical diagnosis 3
• 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
• Do not assume negative imaging excludes endometriosis—superficial peritoneal disease is poorly detected by all imaging modalities 1
• Screen for cardiovascular risk—endometriosis increases stroke risk (HR 1.34) 2

Diagnostic Delay Considerations

Endometriosis diagnosis is frequently delayed due to variable presentation and nonspecific findings. 1, 6 The current imaging-first approach reduces morbidity by enabling better surgical planning and decreasing incomplete surgeries requiring reoperation. 1