[Lymphatics of the thoracic surface of the diaphragm especially located around the inferior surface of the pericardial sac]

Abstract

The lymphatics on the thoracic surface of the diaphragm, especially lying around the lateral and posterior sides of the base of the cardiac sac, were examined in 68 adult Japanese cadavers macroscopically (37 males and 24 females, aged 45-92 years, no clinical evidences of neoplasms). In this observation, a vein which drained into the terminal portion of the inferior vena cava was observed. The lymph nodes in this region were located along the vein frequently (80.9%). The vein passed through the esophageal hiatus, or penetrated the diaphragm and finally communicated with veins around the esophagogastric junction. However, lymphatic vessels were not observed passing through the phrenico-esophageal membrane and/or the diaphragm. The collecting vessels, which originated from the lymphatics, drained into the esophageal lymphatics, and it drained into the thoracic duct via the esophageal lymphatics. In pleural effusion cases, lymphatic nets were clearly observed on the thoracic surface of the diaphragm immediately under the parietal pleura. The lymphatic nets did not communicate with the diaphragmatic lymphatics around the base of the cardiac sac. Moreover, large collecting vessel from the lymphatic nets passed through the muscular crus of the diaphragm near the medial arcuate ligament and traveled inferior to merge at the original portion of the thoracic duct at the level of the renal vessels. From these observations, the lymphatics on the posterior part of the thoracic surface of the diaphragm communicated with several regional lymphatics independently. This morphological lymphatic traveling suggests that the route differs in cases of pleural effusion or cancer metastasis.