azygous lobe of lung

The azygous lobe of the lung is an accessory lobe of the right lung. It is rare and usually associated with an abnormality of the azygous vein. It is produced by an aberrant position of the azygous vein near the hilum of the lung. It divides the right superior lobe near the apex of the lung down to the hilum in roughly the median plane. The fissure created, the meso-azygous fissure, is lined by both visceral and parietal pleura. The lobe lies superomedial to the fissure.