IS Case 166: Azygos lobe

Chandler Shyu, MD, MPH

Imaging Sciences URMC 2008
Publication Date: 2009-05-21


Patient is an 11-year-old male with motor vehicle trauma. CT chest, abdomen, pelvis performed in Emergency Department (ED).


Chest CT demonstrated a well-defined curvilinear line at the right apex denoting the normal variant azygos lobe.


Azygos lobe


Azygos lobe is an accessory lobe at the right apex that frequently presents as an incidental finding. There is no clinical significance and no treatment is required. Prevalence is around 1% of the general population.

On chest radiograph, azygos lobe can be seen as a curvilinear line of the right apex separating the apical right upper lung segment. CT better demonstrates the accessory lobe and the curvilinear line which represents the infolding of the pleura at this level. Developmentally, the azygos lobe results when the right apical bronchus grows medial to the azygos vein.


  1. Mata J, Cáceres J, Alegret X, Coscojuela P, De Marcos JA. Imaging of the azygos lobe: normal anatomy and variations. AJR Am J Roentgenol. 1991 May;156(5):931-7. [PMID: 2017954]

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