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The pleural lymphatic system has a great absorption capacity. Its most known function is fluid resorption. The pleura which cover the lungs (visceral pleura), the mediastinum, diaphragm and thoracic wall (parietal pleura) are formed by a mesothelial cell layer (mesothelium). This permeable layer is in direct contact with the vascular endothelium. The mesothelium is based over a connective tissue (interstitium) containing the blood and lymphatic vessels. The primary lymphatic vessels drain interstitium but are also in direct contact with pleural space by the stoma or openings, situated in the lower parts of parietal pleura, i.e: diaphragm, over lower ribs and mediastinum but not existing in the adjacent visceral pleura. In addition, a part of interstitial pulmonary fluid entered in the pleural cavity by passing the visceral pleura would be absorbed by these openings. The resorption process is active and directly related to the function of smooth muscles of lymphatic vessels. Besides resorption, we must emphasize that this "pumping" activity is permanent and the origin of negative pressure (the pleural void) in pleural cavity, a unique property. The other resorbed elements are molecules, bacterial and cellular debris, cells, red blood and cancer cells., (Copyright © 2013. Published by Elsevier Masson SAS.)

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.

The lymphatic drainage of the pericardium may have a prognostic value in lung cancer and its anatomical pattern was the purpose of this study. The lymphatic vessels of the pericardium were visualized on 12 fresh adult human cadavers by injection of a green colorant by means of the classical equipment for pedal lymphography. Seventeen injections were performed on the right side and 22 injections on the left side, visualizing 20 and 29 lymphatic pathways respectively. Whatever the side injected, the lymphatic vessels mainly directed toward the tracheobronchial nodes (n = 35) and less frequently toward the prepericardial lymphatic vessels and nodes (n = 14). Such results demonstrate the aggravating role played by the lymphatic drainage in the prognosis of the lung cancers invading the pericardium.

The prognosis of non small cell lung cancer (NSCLC) invading the diaphragm is poor, probably due to the richness of the lymphatic drainage of the diaphragm. The aim of this study was to determine mediastinal lymphatic efferents from the diaphragm. The diaphragms of 20 adult cadavers (77-104 years) were injected with a dye (modified Gerota's medium) to permit the lymph vessels to be catheterised and then dissected. Each stage of the dissection was described and photographed: 23 injections on the right and 25 on the left. Diaphragmatic lymph vessels passed to one of three lymph centres: posterior (paraaortic nodes, n = 16), anterior (juxtasternal nodes, n = 16) and mediastinal (visceral nodes, n = 16). From these lymph centres arose ascending lymph pathways: posteriorly to the thoracic duct (8/16), anteriorly along the internal thoracic vessels (10/16) and in the mediastinum to the peritracheobronchial nodes (6/10). Lymphatics from the diaphragm are abundant and drain towards mediastinal node lymph centres connecting to the blood stream via the thoracic duct. These lymph pathways are common with those of the pulmonary segments. Poor prognosis of NSCLC invading the diaphragm may be explained by the common lymphatic drainage of both the lung and diaphragm.

In its anatomy and physiology the pig is comparable with humans and its organs can be considered for xenotransplantation. We have studied the lymphatic drainage of the heart and lungs in 15 pigs. A coloured mass was injected into the myocardium and/or beneath the visceral pleura. The first nodes coloured were directly injected again. No lymph node was observed inside the heart and lungs. The first lymph nodes coloured were the peritracheobronchial nodes. There was no node in front of the thoracic trachea (Barety's compartment in man). Left suprabronchial nodes were connected with the thoracic duct in the mediastinum. The lymphatics of the heart and lungs in the pig are similar to those of human. Phylogenesis explains "skipping" metastases and the significance of N1 disease in lung cancer, as well as chylothorax occurring after heart and lung surgery.

The aim of this study was to describe in detail the anastomoses between the pulmonary lymphatic vessels and the veins of the neck so as to better understand their role in certain aspects of thoracic surgery. The lymphatic vessels of 687 pulmonary segments in 360 cadavers were injected. A detailed study of the proximal end of the right paratracheal, right tracheo-esophageal, left preaortocarotid and left recurrent lymph node chains was undertaken. The results showed the absence of any major right lymphatic "vein". There were, however, many lymphatic arches draining into the jugulo-subclavian confluence ipsilaterally, and, in 10 to 15% of cases, contralaterally as well. The intertracheobronchial lymph nodes also drained into the venous confluence of the neck via direct lymphatic vessels, without lymph node relays. Finally, the left mediastinal lymph node chains were frequently found to drain into the arch of the thoracic duct (40% of cases), and reflux due to valvular incompetence at this level may account for chylous pericarditis and some cases of chylothorax after surgery.

The aim of this study was to describe in detail the anastomoses between pulmonary lymphatic vessels and veins of the neck so as to better understand certain complications in thoracic surgery. Lymphatic vessels of 687 pulmonary segments in 360 cadavers were injected. Detailed study of the end of the right paratracheal, right thoraco oesophageal, left preaorticocarotid and left recurrent lymph node chains was undertaken. The results showed the absence of any major right lymphatic duct. There were, however, many lymphatic arches draining into the jugulo-subclavian confluent ipsilaterally and, in 10 to 25% of cases, contralaterally, as well. The intertracheobronchial lymph nodes also drained into the venous confluents of the neck, via direct lymphatic vessels, without lymph node relays. Lastly, the left mediastinal lymph node chains were frequently found to drain into the arch of the thoracic duct (40% of cases), and reflux by valvular incompetence at this level could be an explanation for chylous pericarditis and some chylothoraxes after surgery.

Correlation of the anatomic and surgical features in 360 cadavers and in 260 patients operated for bronchial carcinoma reveals that the lymphatics of the lung reach the ipsilateral mediastinum, sometimes directly and sometimes by sites which do not correspond to the anatomic site of the injection or of the pulmonary lesion. This implies the need for systematic eradication of all the lymph nodes of the ipsilateral mediastinum during surgery for bronchial carcinoma. In cases of tumoral lesions (N2), the prognosis is better when only one site is involved, whether the nodal disease is microscopic, uni- or multiglandular, with or without rupture of the capsule and whatever treatment is carried out, even when resection seems macroscopically complete to the surgeon. This is explicable in the light of the anatomic study, which shows that the lymph node chain is a functional entity which channels the lymph into the systemic circulation, either at the venous confluence of the neck or into the thoracic duct in the mediastinum. When only a single chain is affected, there is a greater than 70% chance that systemic metastases are already present, 90% when N2 affects 2 chains, while in N3 cases (lymph passage to contralateral chains) the incidence reaches virtually 100%. However, macroscopically satisfactory excision allows management of the local problem, and involvement of the mediastinal nodes, even with capsular rupture, cannot be considered as a contraindication in the absence of clinically detectable systemic metastases.

The study was carried on 65 cadavers: 50 adults and 15 newborns. The esophagus was injected at the level to the neck 16 times, in the thorax at the superior level 18 times, middle level 30 times and inferior level 21 times. The lymphatic pathways were named short when joining the nodes at the same level, half long when joining the nodes of the neighbouring level, long when joining third level, and very long. At the level of the neck were injected 24 lymph nodes chains: in 12.5% of the cases the pathways were long, joining the nodes of the arch of the Azygos vein. At the superior thorax level were injected 27 chains: half of the pathways were half-long: 7.5% long (-joining the pharynx once and the cardia once). At the middle thorax level were injected 37 chains: 27% were long and very long. At the inferior thoracic level were injected 21 chains: The pathways were half long in half cases and very long in 15% of the cases joining the cervical nodes. These results compare with experience in oncology and justify the need for total esophagectomies and nodes resection of all levels in surgical treatment of carcinomas of the esophagus.

Lymphatic spread of carcinoma of the lung to the mediastinum is an essential factor determining prognosis. An anatomic study of the mediastinal lymph nodes was made on 360 cadavers of adult subjects based on injection of the pulmonary segment. Eleven anatomic sites were involved. In 20 to 40% of cases the lymph reached these sites without any relay in the intrapulmonary lymph nodes. Within these sites the lymph flow continued towards the systemic circulation by traversing a variable number of lymph nodes, or sometimes none. The lymph flow reached the venous circulation in the neck, but in more than one case in ten the lymph had already entered the thoracic duct in the mediastinum, and in an intermediate number of cases the sites in the opposite mediastinum.

The study was carried out on 91 adult cadavers to point out clearly the lymphatic drainages of the heart into the blood circulation. 45 right and 63 left ventricles and 9 right and 5 left atria were injected by means of a green modified gerota medium. A right collecting trunk received its afferents from 29 right and 5 left ventricles, ran upwards in front of the ascending aorta, involved the left brachiocephalic nodes and opened into the left subclavicular veins but also in 1 case in 5 into thoracic duct. A left collecting trunk received its afferents from 59 left and 23 right ventricles, ascended along the pulmonary trunk, involved the right paratracheal nodes and opened into the right subclavicular veins. From the right paratracheal nodes were also injected the left tracheobronchial nodes in 14 cases, and then the left brachiocephalic nodes twice, the left paratracheal nodes in 3 cases until the thoracic duct once and directly the thoracic duct in the mediastinum in one case. Afferents from the right atria ran upwards the superior vena cava and involved the right brachiocephalic nodes but connected also with the right paratracheal nodes as did the afferents of the left atria too. The connections with the thoracic duct must be emphasized.

Lymph nodes of the Barety's space (LNLB) often involved in lung diseases are known under various names for a long time ago by pathologists. Our study involves 360 cadavers of adult subjects. The injection of a dye was performed by direct catheterization of a pulmonary segment. L.N.L.B. were directly or indirectly coloured (inter connected ganglionary network) more often from the lobes of the right lung, but from the lobes of the left lung too. From L.N.L.B. the lymphatic flow discharges in the venous confluent of the neck in the right side; in 1/4 of the cases a mediastinal efferent joints the left venous confluent too. From the lower lymph nodes of the space efferents can go to lymph nodes which are located right along the arch of the azygos vein (and then to the thoracic duct) and in the left side the group of left suprabronchial lymph nodes (then either to the thoracic duct in the mediastinum, or to the recurrent chain to the neck). At last, it seems that inside the lymph nodes themselves, lymphatic flows exist, the topography and the nature of which change according to the area interested by the injection.

Anatomical descriptions of the pulmonary lymphatics come mostly from data collected on the fetus or the newborn. Few studies refer to the respective drainage of the different segments, owing to their recent identification. However, the surgeon operating a lung must know whether a given region can drain directly into the mediastinal lymph nodes, and where exactly it drains. Clinical observations tend to favour this possibility. In fact, it is not rare that tumors considered as N.O., that is without any involvement of hilum lymph nodes recur in the mediastinum. In addition, the systematic excision of mediastinal lymphatic chains, being carried out by out surgical team for more than 2 years, has shown the presence of mediastinal nodes in a lot of tumors of this type. The anatomical study which started 8 months ago is presented here and fully confirm this theory. Il showed the presence of collectors leading directly to the mediastinal lymph nodes, the possibility of contra-lateral drainage and of ducts leading directly to the supra-clavicular regions.

The subpleural lymphatics of 483 lung segments were injected in cadavers of 260 adult subjects. The injected lymph vessels corresponded to the pulmonary segmentation in 91% of the cases and remained close by in the other cases. Direct passages to the mediastinal nodes were observed in 54 of 243 right lung segments injected (22.2%) and 60 of 240 left lung segments (25%). Among a total of 114 direct passages observed, 99 remained superficial in the pleura, half of them composed of a single vessel. These passages have been observed more frequently in the segments of the upper lobes. Injections of basal segments in the right and left lower lobes showed fewer of these direct passages to the mediastinal lymph nodes and also demonstrated direct lymph vessels to lymph nodes located at the origin of the upper lobar bronchi. In two dissections of the right upper lobe, the drainage went directly to the right venous jugular-subclavian junction, and in three dissections from three right terminal basal segments the lymph vessel went directly to the thoracic duct in its mediastinal passage. Direct contralateral lymph pathways were observed five times, four of them from basal segments of lower lobes.