Will endometriosis show up on ultrasound?

Ultrasound Detection of Endometriosis

Standard ultrasound alone is not sufficient to detect all forms of endometriosis, but specialized transvaginal ultrasound protocols performed by experts can identify many forms of endometriosis, particularly endometriomas and deep infiltrating endometriosis. 1

Types of Endometriosis Visible on Ultrasound

Reliably Detected on Ultrasound:

• Ovarian Endometriomas: Appear as adnexal or ovarian masses with homogenous low-level internal echoes. The presence of echogenic foci in the wall (hemosiderin deposits) or multilocularity increases likelihood of endometrioma diagnosis 1
• Deep Infiltrating Endometriosis (DIE): Can be detected with specialized transvaginal ultrasound protocols when performed by experienced operators 1
• Rectosigmoid Endometriosis: Specialized TVUS has shown superior detection compared to MRI in some studies 1

Limited or Poor Detection on Ultrasound:

• Superficial Peritoneal Endometriosis: Cannot be reliably detected on ultrasound 2
• Small Endometrial Implants: Often missed on standard imaging 2

Diagnostic Accuracy by Location

The accuracy of ultrasound for detecting endometriosis varies significantly by location:

• Ovarian Endometriomas: High sensitivity and specificity (positive likelihood ratio >10) 3
• Rectovaginal Endometriosis: Moderate sensitivity, high specificity 3
• Bladder DIE: Very high sensitivity and specificity (negative likelihood ratio <0.1) 3
• Uterosacral Ligament DIE: Lower sensitivity but high specificity 3

Specialized Ultrasound Techniques Required

Standard pelvic ultrasound is insufficient for comprehensive endometriosis evaluation. The American College of Radiology recommends:

1. Expanded Protocol TVUS: Includes detailed imaging of uterosacral ligaments, anterior rectosigmoid wall, appendix, and diaphragm with dynamic sliding maneuvers to evaluate organ mobility 1

2. Preparation Requirements:

   • Bowel preparation or enema for detection of bowel lesions 1
   • Some protocols include 3D ultrasound imaging and saline contrast sonovaginography 1

3. Expertise Requirement: Special training is required with a learning curve of at least 40 examinations 1

Important Clinical Considerations

• False Negatives: Negative ultrasound findings are less reliable than positive findings. Patients with significant symptoms may still benefit from further investigation even with normal ultrasound results 3

• Operator Dependency: Studies comparing trained versus untrained operators showed that the modality predicted bowel endometriosis only when performed by trained operators 1

• Diagnostic Algorithm:

  1. Start with transvaginal ultrasound by an experienced operator using expanded protocol
  2. If ultrasound is negative but symptoms persist despite medical therapy, consider laparoscopy 2
  3. For cases requiring further characterization, MRI pelvis without and with IV contrast may be appropriate 1

Limitations and Pitfalls

• Standard TVUS has significantly lower sensitivity compared to expanded protocol TVUS studies 1
• Expanded protocol TVUS studies are not widely available in the United States 1
• Differential diagnosis can be challenging as several gynecological and non-gynecological conditions can mimic deep-infiltrating endometriosis 4
• Distorted anatomy secondary to adhesions and fibrosis presents major difficulties during complete sonographic evaluation 4

In summary, while specialized ultrasound can detect many forms of endometriosis, particularly endometriomas and deep infiltrating disease, it cannot reliably detect all forms of endometriosis, especially superficial peritoneal disease. The diagnostic accuracy depends heavily on the location of lesions, the ultrasound protocol used, and the expertise of the operator.