<prompt> Bilateral rib notching is seen inCoarctation of aortaPDATAPVCAll of the above  <response>: Radiological features of COAReverse figure of 3 sign or double bulge sign or E sign on the left border of aortic shadow is formed by above downward:- Prestenotic dilatation; coarctation itself indentation; poststenotic dilatation.Double aortic knuckle.Docks sign:- There is bilateral notching of inferior margins of 3-8 ribs. Rib notching is absent in the 1st 2nd ribs because first and second intercostal arteries do not take part in the collateral circulation. Rib notching increases with age and after the age of 7 years, rib notching is present in almost all the cases. 