Lymphatic drainage of lung segments in the visceral pleura: a cadaveric study

Although peribronchial lymphatic drainage of the lung has been well characterized, lymphatic drainage in the visceral pleura is less well understood. The objective of the present study was to evaluate the lymphatic drainage of lung segments in the visceral pleura. Adult, European cadavers were examined. Cadavers with a history of pleural or pulmonary disease were excluded. The cadavers had been refrigerated but not embalmed. The lungs were surgically removed and re-warmed. Blue dye was injected into the subpleural area and into the first draining visceral pleural lymphatic vessel of each lung segment. Twenty-one cadavers (7 males and 14 females; mean age 80.9 years) were dissected an average of 9.8 day postmortem. A total of 380 dye injections (in 95 lobes) were performed. Lymphatic drainage of the visceral pleura followed a segmental pathway in 44.2% of the injections (n = 168) and an intersegmental pathway in 55.8% (n = 212). Drainage was found to be both intersegmental and interlobar in 2.6% of the injections (n = 10). Lymphatic drainage in the visceral pleura followed an intersegmental pathway in 22.8% (n = 13) of right upper lobe injections, 57.9% (n = 22) of right middle lobe injections, 83.3% (n = 75) of right lower lobe injections, 21% (n = 21) of left upper lobe injections, and 85.3% (n = 81) of left lower lobe injections. In the lung, lymphatic drainage in the visceral pleura appears to be more intersegmental than the peribronchial pathway is-especially in the lower lobes. The involvement of intersegmental lymphatic drainage in the visceral pleura should now be evaluated during pulmonary resections (and especially sub-lobar resections) for lung cancer.