Ribnotching of 4-9th ribs with double bulging is seen in -

Ans. is 'c' i.e., Coarctation of Aoa Radiological findings of COA 1. Abnormal Aoic arch : Commonestfinding Site of narrowing may be seen as an identation. Classic '3 sign' or double bulge sign' on left border of aoic shadow is formed by (above downwards) Prestenotic dilatation Coarctation itself (indentation) Poststenotic dilatation 2. Rib notching : is a frequent sign in adults. It is not seen until late childhood. It is seen on the inferior margin of posterior halves of ribs from 3'd or 4th ribs downwards. Rib notching is due to enlargement of intercostal aeries which act as collateral vessels. These collateral vessels produce indentation, on the ribs at the above sites.