Approach to white out lung

When one part of the hemithorax is white in a Chest Xray we have a certain approach to...

When one part of the hemithorax is white in a Chest Xray, we have a certain approach to come to a differential diagnosis. First we need to know the causes of white out lung, and then we can come to a differential diagnosis by looking at these common points.

Causes of unilateral white out lungs are-

  1. Massive pleural effusion.
  2. Unilateral total lung collapse.
  3. Large thoracic mass.
  4. Massive unilateral consolidation.

The approach is as follows:

a. Look at the shift of the mediastinum

  • If the mediastinum and trachea are shifted to the opposite side from the opacity, then this is probably from the large unilateral pleural effusion or mass. Pleural effusions and mass push the mediastinum.
  • If the mediastinum is shifted to the same side, then it is usually from ipsilateral lung collapse. With collapse, there is volume loss of lung, so mediastinum and trachea shift towards the side of collapse to compensate for the volume loss.
  • If the mediastinum and trachea are in the central position, then it is usually from consolidation; or collapse and effusion ( balancing each other); or if there is pleural effusion with pleural based mass ( mesothelioma).

b. Look at the bronchus-

  • If you see patent bronchus and tiny bronchii inside the opacity, it is called air- bronchograms , and it is a sign of consolidation.
  • If the bronchus is cut off abruptly, then it may be some foreign body or mass in the bronchus that has led to the collapse of the unilateral lung. So if you don’t see air bronchogram and you also see that the bronchus is abruptly cut-off , then it is a sign of lung collapse.
  • If the bronchus is patent but displaced towards the opposite side,  and narrowed, then this might be due to massive pleural effusion or pleural based mass.

Other uncommon causes may be:

Removal of a lung ( pneumonectomy). For this take the history of surgery. Sometimes, you will notice sutures in the lungs.

Some examples are given as follows:

Note the abrupt cut- off of the left bronchus( red arrow) with left opaque hemithorax. Also, the trachea has deviated to the left side. This is a case of left lung collapse, probably from pathology in the left main bronchus ( endobronchial growth/ foreign body).

Here we can see both bronchi are compressed ( yellow arrows), Mediastinum is shifted to the left side and the opacity is homogenous on the right side. This is a case of massive right pleural effusion.

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