Azygous lobe: a normal variant of pulmonary anatomy


Azygous lobe: a normal variant of pulmonary anatomy

Stephen Melnick, DO*, Richard Loynd, DO and Dina Khateeb, DO

Department of Internal Medicine, Reading Health System, West Reading, PA, USA

Citation: Journal of Community Hospital Internal Medicine Perspectives 2016, 6: 33776 -

Copyright: © 2016 Stephen Melnick et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License, permitting all non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Received: 10 October 2016; Accepted: 14 October 2016; Published: 15 December 2016

Competing interests and funding: The authors have not received any funding or benefits from industry or elsewhere to conduct this study.

*Correspondence to: Stephen Melnick, Department of Internal Medicine, Reading Health System, West Reading, PA, USA, Email:


The azygous lobe is a normal anatomical variant with reported incidence of 0.2–1.2% (1). We report a case of a 51-year-old man with past medical history significant for drug and alcohol abuse, who presented to the emergency department with altered mental status and hypoxic respiratory failure. Given his altered mental status, history was unable to be obtained. Laboratory workup was positive for opiates and benzodiazepines. Imaging was unremarkable, with the exception of a chest computed tomography (CT) showing an incidental finding of an accessory azygous lobe (Fig. 1).

Fig 1

Fig. 1.   Chest CT with contrast showing the azygous fissure in the right upper lobe.

During embryogenesis, the right posterior cardinal vein (a precursor of the azygous vein) penetrates the right upper lobe of the lung instead of traveling over the apex. This later invaginates and creates what is known as the azygous fissure. This fissure contains the azygous vein which can easily be visible on plain chest films (2).

This anatomical variant (azygous lobe) can also be visible on CT imaging, as a thickened fissure from the posterior vertebral body extending to the superior vena cava. This can be seen in our case.

The azygous lobe formation is a benign process and is often found incidentally. However, it is important for radiologists and surgeons to recognize this, as this can alter the approach for lobectomies or segmental resections (3).


  1. Arakawa T, Terashima T, Miki A. A human case of an azygos lobe: Determining an anatomical basis for its therapeutic postural drainage. Clin Anat 2008; 21: 524–30. Publisher Full Text
  2. Sieber W, Karcara N, Pant P. Pulmonary azygous lobe – An anatomical variant. Kathmandu Univ Med J (KUMJ) 2014; 12(46): 151–2.
  3. Murlimanju BV, Prabhu LV, Shilpa K, Pai MM, Kumar CG, Rai A, et al. Pulmonary fissures and lobes: A cadaveric study with emphasis on surgical and radiological implications. Clin Ter 2012; 163(1): 9–13.
About The Authors

Stephen Melnick
Reading Hospital and Medical Center
United States

Richard Loynd

United States

Dina Khateeb

United States

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