Widened Mediastinum

A mediastinal width of >8cm is abnormal, measured at the level of the carina, though a supine, poorly inspired trauma film may magnify a normal mediastinum. The concern is a haematoma due to an acute thoracic aortic injury, particularly if there is an appropriate mechanism e.g. sudden deceleration in a high speed road traffic collision (RTC) or fall from a height.

Patients with complete rupture rarely survive to x-ray. A high index of suspicion should prompt further imaging to detect those with incomplete and potentially salvageable tears.

Learning bite

CT demonstrates the presence of injuries such as pneumothorax and haemothorax which are easily missed or not visible on the trauma supine chest x-ray. It can also, with contrast, examine mediastinal structures such as the aorta. Have a very low threshold for scanning the chest in patients with major trauma.

Possible x-ray signs include:

Widened mediastinum (56-63%)

Abnormal aortic contour (48%)

Aortic knuckle double calcium sign >5mm (14%)

Pleural effusion (L>R)

Tracheal shift

Left apical cap

Deviated NGT.

‘Normal’ in 11-16%.

Reference

Life in the Fastlane: Acute Aortic Dissection