Large Pleural Effusion

General Considerations

• There are three major causes of an opacified hemithorax (plus one other that is less common). They are:
• Atelectasis of the entire lung
• A very large pleural effusion
• Pneumonia of an entire lung
• And a fourth cause:
• Pneumonectomy – removal of an entire lung 

Massive Effusion

• If fluid, whether blood, an exudate or a transudate, fills the pleural space so as to opacify almost the entire hemithorax, then the fluid acts like a mass compressing the underlying lung tissue.
• When enough pleural fluid accumulates, the large effusion “pushes” mobile structures away and there is a shift of the heart and trachea away from the side of opacification
• Massive pleural effusions are frequently the result of malignancy, either in the form of a bronchogenic carcinoma or secondary to metastases to the pleura from a distant organ.
• Trauma can produce a hemothorax and Tuberculosis is notorious for causing large, clinically silent effusions.
• The effusions from congestive heart failure, while very common, are most often bilateral (but asymmetrical) and they rarely grow large enough to occupy an entire hemithorax.
• At times, there may be a perfect balance between the push of a malignant effusion and the pull of underlying obstructive atelectasis from the malignancy itself. 
• In an adult patient with an opacified hemithorax, no air bronchograms and little or no shift of the mobile thoracic structures, it is important to suspect an obstructing bronchogenic carcinoma, perhaps with metastases to the pleura. A CT scan of the chest will reveal the abnormalities.

 

Recognizing a “Shift” in Pleural Effusion
Structure	Normal position	Right-sided Effusion	Left-sided Effusion
Heart	Midline	Heart moves leftward; apex may lie near chest wall	Heart moves rightward; more of heart protrudes to right of spine
Trachea	Midline	Shifts toward left	Shifts toward right
Hemidiaphragm	Right higher than left	Right hemidiaphragm disappears on chest radiograph (silhouette sign)	Left hemidiaphragm disappears on chest radiograph (silhouette sign)

 

    
Large Right Pleural Effusion. There is complete opacification of the right hemithorax with a right-to-left shift of the trachea (black arrow) and the cardiac apex (white arrow) due to the "mass-like" effect of the effusion. The effusion was caused by an underlying bronchogenic carcinoma.