The ductus arteriosus is a normal fetal structure arising from the left sixth aortic arch. It is a vascular connection between the main pulmonary artery and the upper descending thoracic aorta that penetrates the pericardium and just distal and opposite to the origin and insertion of the left subclavian artery. The anatomy of the thorax is essential to identifying and safely closing a PDA as several important structures surround the ductus. The left vagus trunk enters the chest from the root of the neck in a groove between the left subclavian artery and the left common carotid artery, crosses the aortic arch as well as the ductus and continues downward. The recurrent laryngeal branch curves around the ductus arteriosus posteriorly and extends back upward into the neck over the surface of the esophagus. The left phrenic nerve enters the thorax medial to the vagus nerve and continues downward on the pericardium. The pericardium encompasses the pulmonary artery end of the ductus arteriosus.