How to diagnose endometriosis?

Diagnosis of Endometriosis

The definitive diagnosis of endometriosis requires laparoscopy with histological confirmation, but transvaginal ultrasound (TVUS) should be used as the first-line imaging modality, with MRI reserved for cases with indeterminate findings or for surgical planning of complex cases. 1, 2

Clinical Presentation

Endometriosis affects approximately 10% of individuals assigned female at birth and presents with various symptoms:

• Pelvic pain (most common symptom)
  • Dysmenorrhea (painful periods)
  • Dyspareunia (painful intercourse)
  • Dyschezia (painful bowel movements)
  • Dysuria (painful urination)
• Menorrhagia (heavy menstrual bleeding)
• Infertility (affects approximately 50% of patients) 1

The correlation between symptoms and disease stage is often poor, making clinical diagnosis challenging 3.

Diagnostic Algorithm

Step 1: Clinical Assessment

• Evaluate for classic symptoms: cyclic pelvic pain, dysmenorrhea, dyspareunia
• Assess for infertility (present in 20-30% of cases)
• Note: Physical examination findings are often nonspecific 1

Step 2: Initial Imaging

• Transvaginal ultrasound (TVUS) - first-line imaging modality 1, 2

  • Look for:
    • Ovarian endometriomas (homogeneous low-level internal echoes)
    • Echogenic foci in the wall (hemosiderin deposits)
    • Multilocularity
    • Deep infiltrating endometriosis (DIE)
    • Uterosacral ligament involvement
    • Rectosigmoid involvement
  • Special techniques:
    • Uterine sliding sign (for pouch of Douglas obliteration)
    • Assessment of nodules at sites of tenderness
    • Evaluation of ovarian mobility
    • Identification of hypoechoic nodules outside ovaries 2

• Combined transabdominal and transvaginal US may be helpful for comprehensive assessment 1

Step 3: Secondary Imaging (if TVUS is negative but clinical suspicion remains high)

• MRI pelvis without and with IV contrast 1, 2

  • Look for:
    • Endometriomas: high signal on T1-weighted with low signal on T2-weighted images (T2 shading)
    • T2 dark spot sign (93% specificity for endometriomas)
    • Deep infiltrating endometriosis: low signal intensity regions with/without hyperintense foci on T2/T1-weighted images
    • Adhesions: fixed retroversion of uterus, low-signal intensity bands, obliteration of organ interfaces
    • Angulation of bowel loops toward posterior uterine surface
    • Displacement of pelvic free fluid
    • Retrouterine fibrous masses 1

• MRI without IV contrast is adequate for DIE diagnosis, but contrast helps differentiate endometriomas from ovarian malignancies 1, 2

Step 4: Definitive Diagnosis

• Laparoscopy with histological confirmation remains the gold standard 3, 4
  • Direct visualization of endometriotic lesions
  • Biopsy for histological confirmation (endometrial glands and stroma)

Special Considerations

• Transrectal ultrasound can be useful for detecting deep infiltrating endometriosis, with high sensitivity (97%) and specificity (96%) for rectovaginal endometriosis 1

• Laboratory markers like serum CA-125 have limited value and are usually elevated only in advanced stages, making them unsuitable for routine screening 3

• CT is not recommended as an initial imaging modality for endometriosis diagnosis 1, 2

Important Caveats

1. Operator dependence: TVUS effectiveness is highly dependent on operator expertise. An expanded protocol TVUS performed by trained operators has similar diagnostic performance to MRI but requires specialized techniques and training (learning curve of at least 40 examinations) 1, 2

2. Diagnostic limitations: A negative TVUS cannot completely exclude endometriosis, particularly superficial peritoneal disease 2

3. Diagnostic delay: Endometriosis is characterized by considerable diagnostic delay, often taking years from symptom onset to diagnosis 5

4. Laparoscopic correlation: The correlation between laparoscopic observations and histological findings can be low, emphasizing the need for biopsy confirmation 3

5. Preoperative imaging: Preoperative imaging is associated with decreased morbidity and mortality and reduces the need for repeat surgeries by enabling more complete initial surgeries 1