Anatomy of the thoracic duct

Course of the thoracic duct. Although wide anatomic variation exists, in most patients (40 to 60 percent), the left thoracic duct ascends from the cisterna chyli, which is a sac located just anterior to the first or second lumbar vertebra and which receives drainage from the intestinal and two lumbar lymphatic trunks. The thoracic duct passes through the aortic hiatus of the diaphragm into the posterior mediastinum continuing cephalad between the aorta and azygos vein until approximately the level of the fifth thoracic vertebra where it passes behind the esophagus. Below the fifth thoracic vertebra, the thoracic duct is commonly a dual or plexiform duct but it becomes a single 2 to 3 mm duct above that level. The thoracic duct continues cephalad adjacent the esophagus passing posterior to the aortic arch and left subclavian artery. It then arches over the subclavian artery descending to empty either as a single (50 percent) or multiple lymphatic channels into the left subclavian vein near its confluence with the left internal jugular vein. A one-way valve at this location prevents blood from entering the thoracic duct. The right lymphatic duct drains into the right subclavian vein.