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

• A. Rib notching
• B. Kerley B lines
• C. Mediastinal widening
• D. Calcifications of the aorta

Answer: (A)

Rib notching on radiographs reflects the body’s development of collateral blood flow around a narrowed segment of the aorta. In coarctation, the aorta is constricted, usually just after the left subclavian artery, so the upper body maintains high pressure while blood flow to the lower body is reduced. To compensate, the intercostal arteries enlarge and carry more blood from the high-pressure proximal aorta to distal vessels. These enlarged intercostal arteries course along the undersurfaces of the ribs, and their pulsatile flow gradually erodes or indents the inferior borders of the ribs, producing the characteristic scalloped “notches” seen on a chest X‑ray.

Kerley B lines would point to interstitial edema from heart failure, not aortic narrowing. Mediastinal widening can be seen with various mediastinal processes or aneurysm but is not the classic clue for coarctation. Calcifications of the aorta suggest atherosclerotic changes rather than the collateral vascular pattern causing rib notching. The presence of rib notching best explains the diagnosis of coarctation in this radiographic context.