What is the best imaging modality for diagnosing endometritis?

Best Imaging for Endometritis

Transvaginal ultrasound (TVUS) is the best first-line imaging modality for diagnosing endometritis. 1

Understanding Endometritis

Endometritis is an inflammatory condition of the endometrium (the lining of the uterus), which can be acute or chronic. It differs from endometriosis (which is endometrial tissue outside the uterine cavity) and should be approached differently from a diagnostic perspective.

Diagnostic Imaging Algorithm

1. First-line imaging: Transvaginal ultrasound (TVUS)

   • TVUS can detect the characteristic findings of endometritis, including:
     • Thick heterogeneous endometrium
     • Fluid and air within the uterine cavity
     • Possible coexisting pathologies (retained products of conception, hematoma, abscess) 1

2. Add-on imaging technique: Color Doppler ultrasound

   • Should be performed in conjunction with TVUS
   • Helps detect vascularity within a thickened endometrial echo complex
   • Improves specificity and negative predictive value for detecting retained products of conception which may be associated with endometritis 1

3. Second-line imaging: MRI pelvis without IV contrast

   • Consider when TVUS findings are equivocal or further characterization is needed
   • Useful for assessing complex cases or complications 1

Ultrasound Findings in Endometritis

• Thick heterogeneous endometrium (variable thickness)
• Fluid and air within the endometrial cavity (air appears as echogenic foci)
• Possible abscess formation in severe cases
• Endometritis is primarily a clinical diagnosis with nonspecific US appearance 1

Important Considerations

• Endometritis is often a clinical diagnosis supported by imaging rather than diagnosed solely by imaging 1
• TVUS should include both transabdominal and transvaginal approaches for optimal assessment 1
• CT is not recommended as an initial imaging modality for endometritis as there is no relevant literature supporting its use 1

Common Pitfalls to Avoid

1. Misdiagnosis pitfalls:

   • Absence of vascularity on Doppler could represent an avascular retained product of conception rather than ruling out pathology 1
   • Marked vascularity can mimic a pseudoaneurysm, though retained products generally extend to the endometrium, whereas pseudoaneurysm is restricted to the myometrium 1

2. Technical pitfalls:

   • Inadequate bladder filling can limit visualization
   • Insufficient transvaginal approach depth can miss fundal pathology
   • Failure to use both transabdominal and transvaginal approaches may result in incomplete assessment 1

Special Situations

• Postpartum endometritis: TVUS with Doppler is particularly valuable in the postpartum period to differentiate between endometritis and retained products of conception 1
• Chronic endometritis: May have more subtle findings and might require endometrial biopsy for definitive diagnosis

In conclusion, while endometritis remains primarily a clinical diagnosis, transvaginal ultrasound with color Doppler should be the first imaging modality employed when imaging is needed to confirm the diagnosis or assess for complications.