Summary of the findings:

• Large right apical emphysematous bleb
• No pneumothorax
• Lungs clear
• Prior lumbar surgery
• Mediastinum, hila, and heart normal

AP Chest:

Ok. So wait. Isn't that a thin white line in the right upper thorax with no markings above it (orange arrows)?? Wouldn't that be a pneumothorax? Note, however, that the line is flat to concave (not convex, like the lung apex in a pneumothorax) and you also get the sense that this is rounded and has mass effect - typical for an emphysematous bleb.

Here is a side by side comparison of a pneumothorax, an emphysematous bleb, and a skin fold:

In the first panel, the pneumothorax, note the thin, barely perceptible white line convex superiorly with no lung markings above it.

In the middle panel, the bleb margin is concave and somewhat branching - it is not a simple curvilinear line.

Finally, the last panel represents a skin fold. Note the appearance is a gradation from dark line to broad ill defined white line. Also note that lung markings are seen superior to the skin fold (orange box). Skin folds are also not anatomic, and they may extend beyond the margin of the thorax.

So what do you do if you are unsure if what you are seeing is a pneumothorax (you certainly don't want to stick a chest tube into an emphysematous bleb or normal lung)?

You could get a CT, and while definitive, takes time and resources. Maybe you are in clinic and don't have access to a CT.

There are two x-ray techniques you can do:

First, inspiratory and expiratory views. The pneumothorax size will increase on the expiratory view. The bleb won't change, nor will the skin fold (which may not actually be present on the repeat x-ray anyway)

Second, which is my favorite, is obtain a decubitus view. Since air floats, you want the affected side UP and the unaffected side down. If there is a pneumothorax, you will see air along the margin of the lateral hemithorax, a bleb won't change.

Diagnosis: Right apical emphysematous bleb