What is an Empyema?

Empyema is a collection of pus in the space between the lung and the chest wall, called the pleural space.  An empyema can be visualized on imaging studies of the chest like a X-ray or CT.  This condition usually develops as a complication of pneumonia, lung abscess, or surgery. Early detection is important because untreated empyema can lead to severe illness.

How Imaging Helps Diagnose Empyema

Medical imaging plays an important role in diagnosing empyema. When patients present with persistent fever, chest pain, and difficulty breathing, doctors often order chest X-rays, CT scans, or ultrasound to evaluate the lungs and pleural space.

Chest X-Ray Findings in Empyema

A standard chest X-ray is often the first imaging test. It can show fluid in the pleural space, but it may not distinguish between simple pleural effusion (fluid buildup) and empyema. Key findings on a chest X-ray include:

• Blunted Costophrenic Angle: A sign of fluid in the pleural space.
• Loculated Pleural Effusion: Fluid that does not shift with patient positioning, which may suggest empyema.
• Split Pleura Sign: Thickening of the pleura on both the lung and chest wall, visible on lateral X-rays or CT scans.

CT Scan for Empyema: The Gold Standard

A CT scan of the chest provides more detail than an X-ray and is considered the most reliable imaging method for diagnosing empyema. Radiologists look for:

• Fluid with Septations: Thin bands dividing the infected fluid, which is highly suggestive of empyema.
• Thickened Pleural Lining: Inflammation causes the pleura to become thick and contrast-enhancing.
• Air Bubbles in the Fluid: This may indicate the presence of gas-forming bacteria.

In my practice, I often see cases where a CT scan clarifies chest X-ray findings especially when distinguishing between empyema and a simple pleural effusion. The presence of pleural thickening and septations points toward empyema rather than a benign fluid collection.

Ultrasound: A Bedside Tool for Diagnosis

A thoracic ultrasound is particularly useful when immediate imaging is needed, such as in critically ill patients. Key ultrasound findings include:

• Complex or Septated Fluid: Unlike simple effusion, empyema appears as an irregular, multilayered collection.
• Echogenic (Dense) Pus-Like Fluid: The infected fluid appears brighter compared to normal pleural fluid.
• Lack of Free Movement: Unlike simple pleural effusion, empyema fluid is often trapped due to inflammatory adhesions.

Causes and Risk Factors for Empyema

Empyema can start from a pneumonia that does not resolve completely with infection spreading to the pleural space. Other risk factors include:

• Lung Infections: Bacterial pneumonia, tuberculosis, or lung abscess.
• Recent Surgery or Trauma: Post-surgical infections, particularly after lung or chest procedures.
• Weakened Immune System: Conditions like diabetes, cancer, or chronic lung disease increase the risk.

Treatment: How Doctors Manage Empyema

Once diagnosed, empyema requires urgent treatment to prevent complications. Common approaches include:

• Antibiotics: To fight the infection.
• Chest Tube Drainage (Thoracostomy): A tube is inserted to remove infected fluid.
• Surgical Intervention: In severe cases, procedures like video-assisted thoracoscopic surgery (VATS) or decortication (removing the thickened pleura) may be necessary.

The Importance of Early Detection on Imaging

Radiologists play an important role in recognizing empyema early, allowing doctors to start treatment before complications arise. When reviewing scans, we look for signs that suggest worsening infection, such as increasing pleural thickening or increasing pockets of pus. Quick diagnosis can make a significant difference in patient recovery.

Conclusion

Empyema is a serious lung infection that requires prompt treatment. Imaging studies, particularly CT scans, are important for accurate diagnosis. Radiologists look for key signs like septated fluid, thickened pleura, and air bubbles to distinguish empyema from other lung conditions. Early detection on imaging leads to faster treatment and better outcomes for patients.

References:

1. https://my.clevelandclinic.org/health/diseases/24269-empyema
2. https://www.ncbi.nlm.nih.gov/sites/books/NBK544279/
3. https://www.jtcvs.org/article/S0022-5223(17)30152-6/fulltext