A 19-year-old man with upper limb hypertension and weak femoral pulses undergoes contrast-enhanced CT of the chest. Imaging shows a short segment narrowing of the distal thoracic aorta just distal to the origin of the left subclavian artery, with dilated internal mammary and posterior intercostal arteries. Which radiographic sign corresponds to the collateral pathway seen here?

• A Bilateral lower lobe septal lines
• B Superior rib notching due to enlarged anterior intercostal arteries
• C Widening of the right paratracheal stripe
• D Inferior rib notching due to enlarged posterior intercostal arteries ✓

Explanation

In coarctation, blood bypasses the narrowed segment via the subclavian arteries and dilated internal mammary and posterior intercostal arteries. Enlarged tortuous posterior intercostal arteries erode the undersurfaces of the ribs, producing inferior rib notching classically involving the third to eighth ribs. The first two intercostal spaces are supplied by the supreme intercostal artery from the costocervical trunk, so they are spared. Superior rib notching is seen in hyperparathyroidism and other causes.

Reference: Grainger and Allison's Diagnostic Radiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.