What is the initial diagnostic test for endometriosis in a woman of reproductive age presenting with symptoms such as pelvic pain, dysmenorrhea, or infertility?

Initial Diagnostic Test for Endometriosis

Transvaginal ultrasound (TVUS) is the initial diagnostic test for suspected endometriosis, with expanded protocol TVUS being the preferred approach when available. 1

Clinical Diagnosis Framework

The diagnosis of endometriosis is fundamentally clinical and does not require surgical confirmation before initiating treatment. 1 However, imaging plays a critical role in identifying deep infiltrating disease that may require specialized surgical planning. 1

Key Clinical Features That Establish Suspicion

• Dysmenorrhea, dyspareunia, dyschezia, dysuria, or chronic pelvic pain are the primary pain patterns associated with endometriosis. 1
• Infertility is present in approximately 50% of patients with endometriosis. 1
• Physical examination findings include nodularity, fixed retroverted uterus, or tender uterosacral ligaments. 1

Initial Imaging Algorithm

First-Line Imaging: Transvaginal Ultrasound

• Standard TVUS has 82.5% sensitivity and 84.6% specificity for endometriosis detection. 1
• Expanded protocol TVUS demonstrates excellent performance for deep endometriosis detection and is comparable to MRI. 1
• The expanded protocol includes evaluation of uterosacral ligaments, assessment of anterior rectosigmoid wall, dynamic sliding maneuvers to assess pouch of Douglas mobility, and evaluation of appendix and diaphragm. 1

When to Proceed to MRI

• MRI pelvis without IV contrast should be obtained if TVUS is inconclusive or for surgical planning, with 90.3% sensitivity and 91% specificity for deep pelvic endometriosis. 1
• MRI is particularly valuable when coexisting pathologies like leiomyomas are present, as TVUS sensitivity drops to 33.3% in these cases. 1
• MRI with IV contrast is highly recommended to differentiate endometriomas from ovarian malignancies, though IV contrast is not routinely needed for detecting deep endometriosis itself. 1

Performance by Anatomic Location

MRI demonstrates location-specific diagnostic accuracy: 1

• Intestinal endometriosis: 92.4% sensitivity and 94.6% specificity
• Deep infiltrating endometriosis (posterior locations): 88% sensitivity and 83.3% specificity
• Bladder wall endometriosis: 50% sensitivity and 97.3% specificity

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. 2, 1
• Do not assume negative imaging excludes endometriosis—superficial peritoneal disease is poorly detected by all imaging modalities. 1
• Do not delay empiric treatment while awaiting surgical confirmation—laparoscopy is no longer required before initiating treatment. 1

Rationale for Imaging-First Approach

• Preoperative imaging reduces morbidity and mortality by decreasing incomplete surgeries requiring reoperation. 1
• Identifying deep infiltrating disease that may require bowel or urologic surgery is crucial for surgical planning. 1
• The imaging-first approach enables better patient counseling and multidisciplinary team preparation. 1

Laboratory Testing

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