- On upright CXR
- On decubitus CXR
- On cross-table lateral CXR
- On supine CXR
- If small in size
- If large in size – tension pneumothorax
Approach to the differential diagnosis of the different appearances of pneumothorax:
- CXR upright: gravity drops lung inferiorly and medially and shows distinct pleural edge with no lung markings lateral to it
- CXR decubitus: gravity drops lung inferiorly and shows distinct pleural edge with no lung markings superior to it
- CXR cross-table lateral: gravity drops lung inferiorly and may show pleural edge with no lung markings anterior to it – but does not tell you which side the pneumothorax is on
- CXR supine: gravity drops lung posteriorly and usually fails to reveal pleural edge, air accumulates anteromedially so pneumothorax can manifest itself as increased lucency throughout hemithorax / sharp heart border / deep sulcus sign = increased lucency in costophrenic angle
- Note: if you suspect small pneumothorax on CXR supine get decubitus image with suspected side up to confirm
- Note: tension pneumothorax is diagnosed when there is mediastinal shift which implies underlying tension
Pediatric Imaging 