Anatomy, Thorax, Lung Azygos Lobe

An azygos lobe is a rare, anatomical variant of the upper lobe of the right lung found in approximately 1% of anatomic specimens and 0.4% of chest radiographs . It forms during embryological development when the posterior cardinal vein, the precursor of the upper thoracic segment of the azygos vein, erroneously migrates through the upper lobe of the lung. Normally, the posterior cardinal vein migrates over the apex of the right lung to its final position in the mediastinum. Awareness of this anatomical variant and its characteristic x-ray features is important among clinicians because its presence may be confused for processes such as bulla, masses, or abscesses.