Pneumothorax

What are the common causes of pneumothorax in children?
When would you suspect pneumothorax in a child?
What are the imaging findings of pneumothorax in a CXR?
Case 1:

Child was in a car accident. Brought to the ER in severe respiratory distress.

CXR

Close up : Arrows pointing to displaced visceral pleura.

Right Hydropneumothorax.

One would expect a horizontal line in upright film.

Pediatrics List