Case 1

Hemopneumothorax, left sided, due to a recent stab wound to the chest.

Findings:

1. Air-fluid level in left hemithorax (black arrows)

    

2. Visceral pleural line visible (white arrows)

    

3. Sternal wires from a median sternotomy

The diagnosis can actually be made from the tiny thumbnail image shown above if one notes the air-fluid level at the base of the left hemithorax. A good rule of thumb is that straight lines like this generally represent either a fluid level or an artifact. In this case it represents a hemopneumothorax. We know that it doesn't represent the stomach bubble, because we can see the fluid level in the stomach just inferior to the one in the hemithorax.

The sine qua non of pneumothorax is the visceral pleural line. This can be easily seen on either of the more detailed views of the image above. If the visceral pleural line is not immediately visible on a standard series of chest films, an expiratory PA or lateral decubitis film may demonstrate it.

Various artifactual curvilinear opacities arise from overlying tubes, vascular lines, clothing hair, skin folds, and the scapulae, and can simulate a pneumothorax. Such artifactual lines may extend beyond the inner margin of the chest wall, making it easy to detect their true nature.

Detection of Pneumothorax in the Supine Subject

Many patients, such as those from intensive care units and those with severe trauma can only be radiographed in the supine position. As luck would have it, many of these patients are among those who will suffer the most from an undetected pneumothorax.

In the supine position, air within the pleural space rises to the highest point in the hemithorax, which is in the area of the hemidiaphragm. This makes it less likely that one will see the classic visceral pleural line -- indeed, supine films are relatively insensitive in detecting pneumothoraces (50 - 70 %). One may increase the pickup rate with the use of expiratory radiographs or with CT of the chest. However, it is also useful to learn the following secondary signs of pneumothorax on the supine radiograph:

• Relative transradiancy in the hypochondrial region

   

• Increased sharpness of the adjacent mediastinal margin

   

• Deep and sometimes tongue-like costophrenic sulcus ("deep sulcus sign")

   

• Visualization of the anterior costophrenic sulcus

   

• Increased sharpness of the cardiac borders

   

• Pleural air in the minor fissure

   

• Depression of the ipsilateral hemidiaphragm

Once a pneumothorax has been identified, it is appropriate to estimate its size. Although more precise methods of size estimation have been described, it is sufficient for most clinical purposes to describe them like you would a T-shirt: i.e. small, medium or large.

Causes of Pneumothorax in Adults