Bilateral thoracic ducts with coexistent persistent left superior vena cava.

A case of bilateral thoracic ducts with coexistent persistent left superior vena cava (SVC) was identified in a 77-year-old Japanese female cadaver during dissection in a gross anatomy course. The persistent left SVC began at the lower surface of the left brachiocephalic vein, descended in front of the aortic arch, and drained into the right atrium through the coronary sinus. The right SVC was normal both in size and in position. The azygos vein, receiving the hemiazygos vein, opened into the right SVC. The accessory hemiazygos vein and the left superior intercostal vein united to form a common trunk, which drained into the left SVC. The left and right thoracic ducts began at the level of the 1st lumbar vertebra, ran upwards parallel and anterior to the vertebral column, and terminated at the venous angles of their corresponding sides. There was an anastomotic branch between them. The present case was considered to be very rare, since the persistent left SVC and bilateral thoracic ducts coexisted. The embryologic basis and clinical importance of this case are discussed.