What is the important structure immediately dorsal to it when placing a clamp on the ductus to avoid injury?

Left recurrent laryngeal nerve-the left recurrent laryngeal nerve is closely associated with the aortic arch and the ligamentum arteriosum/ductus arteriosus. as the left vagus nerve passes near the aortic arch, it gives offf the left recurrent laryngeal nerve. this nerve then loops under the aortic arch, lateral to the ligamentum arteriosum, and ascends to the larynx in the tracheoesophageal groove. during surgery to close a patent ductus arteriosus, a surgeon must be careful to protect the left recurrent laryngeal nerve, which is lateral to the duct that is being ligated. the accessory hemiazygos vein is a vein on the left side of the body which drains blood from the left chest wall into the azygos vein. the internal thoracic artery is a branch of the subclavian artery which supplies blood to the anterior chest wall and gives rise to the anterior intercostal arteries. the left phrenic nerve passes through the thorax to innervate the diaphragm. it is a bit lateral to the area where the surgeon is clamping the ductus arteriosus, so it would not be at risk during the procedure. finally, the thoracic duct is found deep in the posterior mediastinum, lying between the aorta and azygos veins.