What is the best imaging modality for diagnosing endometritis?

Best Imaging Modality for Diagnosing Endometritis

Transvaginal ultrasound (TVUS) is the first-line imaging modality for diagnosing endometritis, showing a thickened heterogeneous endometrium with possible fluid and air within the cavity. 1

Understanding Endometritis Imaging

Endometritis is primarily a clinical diagnosis, but imaging can help assess for coexisting pathology and complications. When imaging is needed, the approach should follow this algorithm:

1. First-line: Transvaginal ultrasound (TVUS)

   • Typical findings: Thickened heterogeneous endometrium with fluid and air within the cavity 1
   • Can detect complications such as retained products of conception (RPOC), hematoma, or abscess
   • Superimposed echogenic foci of air suggest infection 1
   • Often performed with transabdominal ultrasound for a complete overview

2. Second-line (if TVUS is indeterminate): MRI pelvis

   • Better for characterizing complex cases or when ultrasound findings are equivocal
   • Can help differentiate endometritis from other conditions with similar ultrasound appearances
   • MRI without contrast is usually sufficient, but contrast may help in complex cases

Ultrasound Technique Considerations

• Combined approach: Transabdominal ultrasound provides anatomic overview while transvaginal approach offers greater contrast and spatial resolution 1
• Color Doppler: Should be included to assess for increased vascularity which may indicate inflammation
• Measurement: Endometrial thickness >8-13mm may suggest pathology 1

Clinical Correlation

It's important to note that endometritis is primarily a clinical diagnosis, and imaging findings should be correlated with:

• Fever
• Uterine tenderness
• Abnormal vaginal discharge
• Elevated white blood cell count

Common Pitfalls and Caveats

• False negatives: Normal imaging does not exclude endometritis, especially early in the disease course
• Differential diagnosis: Similar ultrasound findings can be seen with retained products of conception (RPOC), which may coexist with endometritis 1
• Postpartum considerations: Normal postpartum changes can mimic pathology; clinical correlation is essential
• Air artifacts: Small amounts of intrauterine air can be normal in the postpartum period or after instrumentation

Special Situations

• Postpartum endometritis: TVUS is particularly useful to rule out retained products of conception, which can be a cause or complication of endometritis 1
• Tuberculous endometritis: May show more specific findings such as synechiae or calcifications
• Chronic endometritis: May have more subtle findings than acute endometritis

While MRI provides excellent soft tissue contrast and a wider field of view, TVUS remains the preferred initial imaging modality due to its wide availability, lower cost, lack of radiation, and good diagnostic performance for endometritis.