A CXR shows a '3' sign with notching of the ribs. What is the most likely diagnosis?

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Multiple Choice

A CXR shows a '3' sign with notching of the ribs. What is the most likely diagnosis?

The big idea here is recognizing radiographic signs of coarctation of the aorta. The “3 sign” on chest X-ray comes from narrowing of the aorta just after the left subclavian artery, with dilation on both sides of the constriction, creating a contour that looks like a number three along the aortic silhouette. The notching of the ribs occurs because enlarged intercostal arteries develop as collateral vessels to bypass the narrowed segment, and these enlarged vessels erode the inferior borders of the ribs over time. Together, these findings point to a long-standing coarctation rather than other conditions. Aortic dissection would typically present with acute chest pain and mediastinal widening or an intimal flap; pulmonary hypertension would show enlarged pulmonary arteries and signs of right heart strain; an abdominal aortic aneurysm would show abdominal or groin signs rather than rib notching and the classic “3 sign.”

The big idea here is recognizing radiographic signs of coarctation of the aorta. The “3 sign” on chest X-ray comes from narrowing of the aorta just after the left subclavian artery, with dilation on both sides of the constriction, creating a contour that looks like a number three along the aortic silhouette. The notching of the ribs occurs because enlarged intercostal arteries develop as collateral vessels to bypass the narrowed segment, and these enlarged vessels erode the inferior borders of the ribs over time.

Together, these findings point to a long-standing coarctation rather than other conditions. Aortic dissection would typically present with acute chest pain and mediastinal widening or an intimal flap; pulmonary hypertension would show enlarged pulmonary arteries and signs of right heart strain; an abdominal aortic aneurysm would show abdominal or groin signs rather than rib notching and the classic “3 sign.”

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