How did this occur in utero?
This occurred as the result of an interruption of the dorsal segment of the left arch between the left common carotid and left subclavian arteries with regression of the right ductus arteriosus in the hypothetical double aortic arch.
The aortic arch is on the right side in relation with the trachea.
The aberrant left subclavian artery is the branch that arises from Kommerell diverticulum at the distal end of the aortic arch. These findings are related to a right aortic arch with aberrant left subclavian artery.
Also, there is dilatation of the azygos vein that demonstrates azygos continuation of the IVC. The azygos vein drains in the superior vena cava.
On the sagital MIP projection outlined with arrows is the suprahepatic IVC and the arch of azygos vein draining into the SVC.