Observe the curvilinear radiopacity seen in the medial aspect of the right upper lobe. This is the classic characteristic appearance of an azygos fissure creating what has been referred to as an azygos lobe. The fine radiopaque line present in the right upper lung apex represents the azygos fissure. The radiopaque density at the base of the fissure represents the azygos vein. This fissure creates an accessory lobe that is often referred to as the azygos lobe. This is of no clinical significance to the patient and no further imaging is necessary.