What is the diagnostic approach for a female patient of reproductive age presenting with symptoms such as pelvic pain, heavy menstrual bleeding, or infertility, suspected of having endometriosis?

How to Diagnose Endometriosis

Endometriosis is fundamentally a clinical diagnosis that does not require surgical confirmation before initiating empiric treatment, with transvaginal ultrasound (TVUS) as the initial imaging modality. 1, 2

Clinical Diagnostic Framework

The diagnosis begins by identifying characteristic symptom patterns and physical examination findings, not by rushing to laparoscopy:

Key Symptom Patterns to Identify

• Pain patterns: dysmenorrhea, dyspareunia, dyschezia, dysuria, or chronic pelvic pain 1, 2
• Infertility: present in approximately 50% of patients with endometriosis 1, 2
• Note: 90% of people with endometriosis report pelvic pain 3

Physical Examination Findings

• Specific findings to assess: nodularity, fixed retroverted uterus, or tender uterosacral ligaments 1, 2
• Critical caveat: normal examination does not exclude the diagnosis 2

Imaging Algorithm

First-Line Imaging

Start with transvaginal ultrasound (TVUS) as the initial imaging modality 1, 2:

• Standard TVUS has sensitivity of 82.5% and specificity of 84.6% 1
• For suspected deep endometriosis: use expanded protocol TVUS (requires specialized training) 1, 2
• Expanded protocol TVUS includes: evaluation of uterosacral ligaments, assessment of anterior rectosigmoid wall, dynamic sliding maneuvers, bowel preparation or enema, and evaluation of appendix and diaphragm 1
• Transabdominal ultrasound can be added to widen the field of view for urinary tract and bowel involvement beyond the pelvis 1, 2

Second-Line Imaging

MRI pelvis without IV contrast if TVUS is inconclusive or for surgical planning 1, 2:

• MRI shows 90.3% sensitivity and 91% specificity for deep pelvic endometriosis 1, 2
• MRI performance by anatomic location: 92.4% sensitivity and 94.6% specificity for intestinal endometriosis; 88% sensitivity and 83.3% specificity for deep infiltrating endometriosis in posterior locations (uterosacral ligament, retrocervical, rectovaginal septum, vaginal fornix); 50% sensitivity and 97.3% specificity for bladder wall endometriosis 4, 1
• MRI diagnostic features: endometriomas (high signal on T1-weighted with low signal on T2-weighted images), T2 dark spot sign (93% specificity for differentiating endometriomas from hemorrhagic cysts), deep infiltrating endometriosis (low signal intensity regions), adhesions/cul-de-sac obliteration 4, 1
• Technical optimization: moderate bladder distention and vaginal contrast improve lesion conspicuity 1

When to Add IV Contrast

MRI with IV contrast is highly recommended to differentiate endometriomas from ovarian malignancies 1, 2, but IV contrast is not routinely needed for detecting deep endometriosis itself 4, 1

Alternative Ultrasound Approaches

Transrectal ultrasound can be useful for deep infiltrating endometriosis 4:

• 97% sensitivity and 96% specificity for rectovaginal endometriosis 4
• 80% sensitivity and 97% specificity for uterosacral ligament implants 4
• Limited to a small anatomic area but useful in patients unable to undergo TVUS 4

What NOT to Do: Critical Pitfalls

• Do not rely on standard TVUS alone for deep endometriosis—expanded protocols or MRI are needed 1, 2
• 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 order CA-125 for diagnosis—it has no clinical utility for diagnosis and should not be used for diagnostic purposes 1, 2
• Do not require laparoscopy with histologic confirmation before initiating empiric treatment 1, 2

Role of Surgery in Diagnosis

Laparoscopy is no longer required before initiating empiric treatment 1, 2:

• Surgery is now reserved for definitive treatment rather than diagnosis 1
• Preoperative imaging reduces morbidity and mortality by decreasing incomplete surgeries requiring reoperation 1
• The imaging-first approach enables better surgical planning and informs patient decision-making 1

Diagnostic Delay Considerations

The diagnosis is often delayed by 5 to 12 years after onset of symptoms, with most women consulting 3 or more clinicians prior to diagnosis 3. The current imaging-first approach reduces morbidity by enabling better surgical planning and decreasing incomplete surgeries requiring reoperation 1.

When Imaging is Indeterminate

If TVUS findings are indeterminate, particularly when coexisting pathologies like leiomyomas are present: TVUS sensitivity drops to 33.3% in these cases, making MRI essential 1. MRI has superior sensitivity (78%) and specificity (93%) for adenomyosis diagnosis when ultrasound findings are equivocal 1.