PNEUMOMEDIASTINUM• Def: free air/gas within the mediastinum• Gas origin:– Intrathoracic

• Trachea, bronchi• Esophagus• Lungs• Pleural space

– Extrathoracic• Head & neck injury• Retroperitoneum

• Can lead to pneumothorax, pnemopericardium, pneumoperitoneum

RADIOLOGICAL FEATURES• Subcutaneous emphysema• Hyperlucent lines enhancing mediastinal viscera

& outline lateral heart borders• Continuous diaphragm sign• Ring-around-pulmonary-artery sign• Thymic/spinnaker sail sign• Naclerio’s V sign• Tubular artery sign• pneumopericardium• Extrapleural sign

Subcutaneous emphysema• Lucencies overlying the shoulder

and upper chest (blue circle)• Red arrow: supraclavicular

emphysema• White arrow: air in mediastinum

Enhancement of heart borders

Enhancement on mediastinal structures

Air outlining ascending aorta

Continuous diaphragm sign

Ring around pulmonary artery sign

• Lucent ring around pulmonary artery

Thymic/Spinnaker sail sign

thymus separated from mediastinal structures

Naclerio’s V sign

Air outlining the descending aorta intersects with air outlining the left hemidiaphragm

Tubular artery sign

Air outlining left subclavian artery & left carotid artery

Pneumopericardium

Air between sternum & heart

Extrapleural sign

Air outlining the left hemidiaphragm

CT Scan

Air in supra-aortic, sub-aortic & para-cardiac mediastinum

Air within mediastinum (white arrows)Subcutaneous emphysema (black arrows)

PULMONARY CONTUSION

• Def: injury to the lung parenchyma without laceration (blunt trauma)

• often occur in small children in the absence of fractures due to the high compliance of the chest wall.

• a/w bruising, ribs #, flail chest• Pathology:– Hemorrhage into the lung parenchyma produces

airspace disease

Plain radiograph• Features seen within 6 hours after trauma• Not sensitive, low clinical value– Faint patchy consolidative regions following history of

blunt trauma.• Usually shows rapid improvement with time, signs

of contusion have often resolved within 48 hours• If consolidation > 72 hours, consider:– Aspiration– ARDS– Pneumonia

Blue: alveolar opacitiesRed: associated ribs #

CT Scan

Red: evidence of pulmonary contusionBlue: rib #

• Most sensitive

• Typically seen as focal, non segmental (typically crescentic) areas of parenchymal opacification