On a PA chest radiograph, which observation is most suggestive of a widened mediastinum and potential aortic pathology?

• A. Decreased mediastinal width.
• B. No contour irregularity.
• C. Increased mediastinal width with potential contour irregularities suggesting aneurysm or dissection.
• D. Thickened diaphragmatic contour.

Answer: (C)

Recognize that widening of the mediastinum on a PA chest radiograph can signal aortic pathology, and irregularity of the aortic contour makes this finding more specific. When the mediastinal width is increased, it suggests the aorta may be enlarged or its wall distorted. If the widening also shows contour irregularities, it points toward vascular problems such as an aneurysm or dissection, where the vessel wall is disrupted or bulging. This combination is the most concerning and is the observation that best suggests a potential aortic issue. Decreased width, lack of contour irregularity, or a thickened diaphragmatic contour do not point as strongly to aortic pathology.