Mediastinum

Size

Masses in the mediastinum will cause it to appear widened (Fig 1). CT is often required to diagnose the exact structures involved.

Position

The trachea should lie centrally in the upper mediastinum unless distorted by previous surgery, lung collapse or tension pneumothorax (Fig 2). It will often deviate slightly to the right at the lower end as it passes the aortic knuckle. It bifurcates at the T6 level.

Free air

Free air may outline the medial surface of the pleura in pneumomediastinum (Fig 3).

Click on the x-rays to enlarge.

Fig 1: Right effusion and wide mediastinum	Fig 2: Tracheal deviation to the right due to pneumonectomy	Fig 3: Pneumomediastinum