Which radiographic sign on chest X-ray is associated with coarctation of the aorta?

• A. '3' sign due to proximal and distal dilations.
• B. Widow's sign.
• C. Kent sign.
• D. Spinal sign.

Answer: (A)

The finding on chest X-ray associated with coarctation of the aorta is the “3 sign.” This appears when the aorta has a narrowed segment (the coarctation) with dilation both proximal (before) and distal (after) the narrowing. On a frontal view, these two dilated portions and the narrowed segment together create a contour that looks like the numeral 3. The sign reflects the prestenotic and poststenotic dilation around the obstruction. In later disease, rib notching due to enlarged collateral arteries may also be seen, but the 3 sign is the classic radiographic clue. The other signs listed are not typical features of coarctation on chest radiographs.