Fundamental Radiological Findings: Hemithorax Opacification

OVERVIEW

This page is dedicated to covering the important radiological finding of a hemithorax opacification.

WHAT IS IT?

A hemithorax opacification refers to a finding on a chest X-ray where and entire lung field becomes more difficult for the X-rays to penetrate. This will lead to increased “white” across that entire lung field (it is also called “hemithorax white-out”).

This image shows a hemithorax opacification on the right side. The differential diagnosis for this finding is discussed more below, however this particular example was caused by a large pleural effusion (source)
DIFFERENTIAL DIAGNOSIS FOR THIS FINDING

When seeing a hemithorax opacification, it is important too keep in mind the following possible causes of this finding:

KEY FEATURES TO LOOK FOR WHEN CHARACTERIZING THE FINDING

When seeing a hemithorax opacification, there are a few important radiological features one should look at to try and characterize the finding. These features can help navigate the differential diagnosis above.

Shift of mediastinal structures: different causes of hemithorax opacification will have a different impact on whether or not they shift mediastinal structures/trachea AWAY or TOWARDS the side of the opacification. The etiology of the condition will intuitively cause the shifting of structures in a particular direction.

In this example of hemithorax opacification, the cause of the finding is a pneumonectomy. The airway is shifted toward the side of the opacification (source).
In this example of hemithorax opacification, the cause of the finding is a pneumonectomy. The airway is shifted toward the side of the opacification (source).

Structures shifting away from the opacification are most consistent with conditions such as a pleural effusion.

Structures remaining in the central position are consistent with conditions such as pneumonia

Structures shifting toward the opacification suggest a process such as a pneumonectomy or complete atelectasis.

Air/fluid level or fluid meniscus superiorly: If the lung field is not completely opacified, looking superiorly for a fluid meniscus can be very useful diagnostically. Really this finding would be specific to a pleural effusion.

At the right apex of the lung we can clearly see an air fluid level that strongly suggests that this hemithorax opacification is caused by a large pleural effusion (source).
At the right apex of the lung we can clearly see an air fluid level that strongly suggests that this hemithorax opacification is caused by a large pleural effusion (source).

 

Page Updated: 12.06.2016