What is the diagnostic approach for endometriosis in a reproductive‑age woman presenting with chronic pelvic pain, dysmenorrhea, dyspareunia, dyschezia, dysuria, infertility, or cyclic bowel/bladder symptoms?

How to Diagnose Endometriosis

Endometriosis diagnosis is fundamentally clinical and does not require surgical confirmation before initiating empiric treatment—transvaginal ultrasound (TVUS) with expanded protocol or MRI pelvis should be used for treatment planning and detecting deep infiltrating disease, not as a prerequisite for starting therapy. 1

Clinical Diagnosis Framework

The diagnosis begins with recognizing characteristic symptom patterns and physical examination findings, followed by strategic imaging to map disease extent:

• Pain patterns include dysmenorrhea (menstrual pain beginning before bleeding), deep dyspareunia (especially during menses), dyschezia, dysuria, chronic non-menstrual pelvic pain lasting at least 6 months, and sacral backache with menses 1, 2, 3
• Infertility is present in approximately 26-50% of patients with endometriosis 1, 3
• Physical examination findings may reveal nodularity in the posterior cul-de-sac, fixed retroverted uterus, tender uterosacral ligaments, or site-specific pelvic tenderness—though normal examination does not exclude the diagnosis 1, 3, 4

The depth of endometriotic lesions correlates directly with pain severity, but the type or stage of lesions has little relationship to pain intensity, explaining why minimal disease can cause severe symptoms 2, 5

Imaging Algorithm

First-Line Imaging

• Transvaginal ultrasound (TVUS) is the initial imaging modality of choice, with sensitivity of 82.5% and specificity of 84.6% for endometriosis detection 1
• Expanded protocol TVUS (when available) demonstrates excellent performance for deep endometriosis detection comparable to MRI and 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

Second-Line Imaging

• MRI pelvis without IV contrast is the next step if TVUS is inconclusive or for surgical planning, with 90.3% sensitivity and 91% specificity for deep pelvic endometriosis 1, 6, 5
• MRI with IV contrast is highly recommended to differentiate endometriomas from ovarian malignancies (given the 0.7-1.6% risk of malignant transformation), though IV contrast is not routinely needed for detecting deep endometriosis itself 1, 4
• MRI diagnostic features include endometriomas (T1 hyperintense hemorrhagic foci), T2 dark spot sign, T2 hypointense fibrosis at torus uterinus and uterosacral ligaments, deep infiltrating endometriosis, adhesions, and cul-de-sac obliteration 1
• Technical optimization for MRI includes moderate bladder distention and vaginal contrast to improve lesion conspicuity 1

MRI performance by anatomic location shows 92.4% sensitivity and 94.6% specificity for intestinal endometriosis, 88% sensitivity and 83.3% specificity for deep infiltrating endometriosis in posterior locations, and 50% sensitivity and 97.3% specificity for bladder wall endometriosis 1

Alternative Specialized Imaging

• Transrectal ultrasound can be useful for deep infiltrating endometriosis when available, with 97% sensitivity and 96% specificity for rectovaginal endometriosis, and 80% sensitivity and 97% specificity for uterosacral ligament implants 1

Laboratory Testing

• CA-125 has no clinical utility for diagnosis and should not be used as a diagnostic test 1, 5
• 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, 5

Surgical Diagnosis

• Laparoscopy with histologic confirmation remains the gold standard for definitive diagnosis but is no longer required before initiating empiric treatment 1, 3, 5
• Surgery is now reserved for definitive treatment rather than diagnosis, and is indicated when empiric therapy is ineffective, immediate diagnosis is necessary, or the patient desires pregnancy 1, 5
• Only experienced surgeons familiar with the protean appearances of endometriosis should rely on visual inspection alone; otherwise, peritoneal biopsy should be used for questionable lesions 1

Preoperative imaging reduces morbidity and mortality by decreasing incomplete surgeries requiring reoperation—accurate preoperative mapping of deep infiltrating disease involving bowel or urologic structures is essential for optimal surgical planning and multidisciplinary team coordination 1, 6

Critical Pitfalls to Avoid

• Do not rely on standard TVUS alone for deep endometriosis—expanded protocols or MRI are needed to adequately assess deep infiltrating disease 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—all imaging modalities have poor sensitivity for superficial peritoneal disease, which can still cause significant symptoms 1
• Do not delay empiric treatment while pursuing surgical confirmation—current guidelines support initiating hormonal therapy based on clinical diagnosis alone 1, 3, 7
• Do not ignore coexisting pathologies—when leiomyomas are present, TVUS sensitivity drops to 33.3%, and MRI should be considered 1

Special Considerations

Postmenopausal Endometriosis

Endometriosis is estrogen-dependent and usually regresses after menopause, but can rarely persist or recur in postmenopausal women, likely secondary to scarring or reactivation from postmenopausal hormonal therapy 8, 9

Diagnostic Delay Context

The average diagnostic delay is 5-12 years from symptom onset, with most women consulting 3 or more clinicians prior to diagnosis—the current imaging-first approach combined with acceptance of clinical diagnosis enables earlier intervention and better surgical planning when needed 1, 3, 7