Chest Radiography

Chest X-ray is not a reliable investigation in the diagnosis of aortic dissection and should not delay definitive imaging in patients with a high degree of clinical suspicion where timely diagnosis is critical.

However, chest x-ray is a useful tool more generally in the workup of a patient with acute chest pain and an abnormal chest x-ray is present most of the time in patients with AAD. Thus, it could provide an important clue to the diagnosis. The following radiological signs may be seen in patients with AAD:

A widened mediastinum

A widened mediastinum is likely the most common chest X-ray finding. A widened mediastinum on chest x-ray can occur either from enlargement of the aorta with an extensive false lumen, or rupture of the aorta, typically the arch, into the mediastinum.

In the latter case, the haematoma is often contained within the mediastinum thereby causing widening of this area on chest radiography with loss of the usual contours of the mediastinum.

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An abnormal aortic contour

An abnormal aortic contour is a subtle chest X-ray change that may occur in around half of patients but can be difficult to identify. The aortic contour may be lost if either there is a false lumen created along the ascending aorta and/or arch, or if there is free rupture of these structures into the mediastinum.

With the latter, the haematoma is contained within the mediastinum and obliterates all the usual contours.

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A soft tissue shadow peripheral to a calcified aortic annulus

This is another subtle chest X-ray finding. A soft tissue shadow peripheral to a calcified aortic annulus occurs in a minority of patients.

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A globular heart suggesting a large haemopericardium

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Pleural effusion

A pleural effusion, representing a haemothorax (invariably massive), may be seen. This typically occurs when the dissection process involves the descending thoracic aorta, and when rupture occurs here it is almost always into the left pleural space.

Note however that normal chest radiography is common in patients with aortic dissection, so a normal CXR cannot rule out the diagnosis. CXR sensitivity for aortic dissection is generally estimated at around 60-90% in studies, though even where positive findings exist, these may be subtle and non-specific.