Direct lymphatic drainage of lung segments to the mediastinal nodes

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.