What causes this anatomical variant?
The azygos fissure is caused by the failure of normal azygos vein in migrating over right lung apex
The left-sided no wire pacing device is in situ. Cardiomediastinal contours are unremarkable. Azygos fissure is noted in the right apex. Lungs and pleural space are clear. No pneumothorax or subphrenic free gas.