Background: The thoracic duct (TD) is the main collecting vessel of the lymphatic system. Little is known about the intrathoracic tributaries of the TD, which are named intercostal, mediastinal, and bronchomediastinal trunks. The purpose of the study was to identify the lymphatic tributaries from intrathoracic organs to the thoracic duct.
Methods: The study was performed on 530 adult cadavers. The lymphatics of different organs were catheterized and injected with a dye: lungs (n = 360), heart (n = 90), esophagus (n = 50), and diaphragm (n = 30). The lymphatic tributaries draining the lymph from these organs to the thoracic duct were dissected along their course to the thoracic duct and classified.
Results: The TD tributaries were observed in 147 cases: right lung (n = 46), left lung (n = 69), heart (n = 8), esophagus (n = 13), and diaphragm (n = 11). Connections with the TD were observed at its origin (n = 13), within the mediastinum (n = 87), and at the level of the TD arch (n = 47). Tributaries from the lung issued from lower paratracheal nodes 4 R (n = 14) and 4 L (n = 31), subaortic 5 (n = 4), subcarinal 7 (n = 18), pulmonary ligament 9 (n = 7), upper tracheal 2 L (n = 28), paraortic 6 (n = 11), and celiac nodes (n = 2). Tributaries from the heart connected with the TD in the mediastinum in 1 case (4 L) and with the TD arch in 7 cases. Tributaries from the esophagus connected with the thoracic duct within the mediastinum in 13 cases; anodal routes were frequent (n = 5). The TD tributaries from the diaphragm were observed in 11 cases, always connecting with the TD at its origin.
Conclusions: Injection of intrathoracic organs permits visualization of TD tributaries. These tributaries appear located at unchanging levels. Lymph of intrathoracic organs may thus drain into the general circulation through the TD. The tributaries may represent a potential route for tumor cells dissemination. When incompetent, due to valve insufficiency, they permit chylous lymph to backflow into the intrathoracic lymph nodes. Injury at this level may lead to intrathoracic chylous effusions.