Pericardial Effusion on Lateral Chest Radiograph

Fig. 1. Lateral chest radiograph shows small bilateral pleural effusions. Enlarged cardiac silhouette with abnormal bands of density noted anterior to the heart (between arrows). Of note, this band of density consists of a central soft tissue sandwiched by lucent stripes.
Fig. 2. Sagital CT image of the same patient correlates well with lateral radiograph in Fig. 1. It shows that the 'sandwich' seen anterior to the heart represents pericardial effusion (star) bounded by epicardial and pericardial fat.

Facts

• Pericardial effusion can be transudate or exudate (pus, blood, infection)
• Symptoms depend on the size and rate of accumulation of effusion
• Chest radiography is not diagnostic of pericardial effusion in most cases
• CT and MRI used to assess size and extent of pericardial effusion
• Measurement of pericardial effusion by CT/MRI tends to be larger than in echocardiography
  

Radiographic Signs of Pericardial Effusion
All four signs are sensitive (71-100%) but not specific (12-46%).

• Enlarged cardiac silhouette with sharp margin, "water bottle" silhouette
  
• Pericardial fat stripe (separation of pericardial layers)
  
• Predominantly left-sided pleural effusion
• Increased transverse cardiac diameter compared with previous radiograph

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Reference:
1. Eisenberg MJ, et al. Diagnostic value of chest radiography for pericardial effusion. J Am Coll Cardiol 1993; 22:588-593
2. Guidelines on the Diagnosis and Management of Pericardial Diseases of the European Society of Cardiology. Eur Heart J 2004; 25:587-610