A human case of an azygos lobe: determining an anatomical basis for its therapeutic postural drainage

An azygos lobe of the human lung is one of the most common lung malformations. However, there are only a few anatomical reports concerning the bronchial and blood supply to this lobe. We encountered the azygos lobe in an anatomical dissection course. The azygos lobe of this case was examined macroscopically and lung parenchyma, including alveoli, terminal bronchioles, and bronchial arteries and veins, was partially removed under a stereoscopic microscope. The azygos lobe was situated medial to the superior lobe and superior to the hilum of the right lung. The parietal pleura wrapped around the azygos vein like a mesentery to form the "meso-azygos." Partial removal of the lung parenchyma revealed that the azygos lobe received bronchial branches from the medial components of the apical and anterior branches of the apical segmental bronchus (B(1)a and B(1)b), and that these bronchial branches were bent excessively in a medial direction from the parent bronchial trunk. For therapeutic drainage of secretions from a right azygos lobe, a 45 degrees upright sitting posture with the neck flexed to the right side is recommended, because in this posture the bronchial branches to the azygos lobe assume a more vertical orientation to facilitate greater dependent drainage of this lobe.