Chest Radiology: The Azygous Fissure, a normal variant
Channel: James Smirniotopoulos
Date: 2013-01-18

The Azygous fissure forms when the arch of the azygous vein invaginates into the developing lung, dragging in a double layer of both visceral and parietal pleura.  The resulting fissure is seen as a linear opacity ending in a round or oval opacity that represents the vein itself.