Which radiographic sign is classically associated with coarctation of the aorta?

• A. Notching of the ribs
• B. Rib crowding
• C. Mediastinal widening
• D. Figure of 3 sign

Answer: (D)

Coarctation of the aorta changes the contour of the aorta itself, with dilation both before and after the narrowed segment. On a frontal chest radiograph, these pre- and post-stenotic enlargements surround the narrowed area and create a silhouette that looks like the number three — the figure of 3 sign. This classic appearance directly reflects the abrupt narrowing of the aorta with proximal and distal dilation and is the radiographic hallmark most closely tied to the condition. Notching of the ribs can occur with long-standing disease due to enlarged collateral intercostal arteries, but it’s a secondary finding. Mediastinal widening is nonspecific, and rib crowding isn’t a standard defining sign.