IS case 459: Azygos lobe

Alok Bhatt, MD

University of Rochester

Imaging Sciences URMC 2010
Publication Date: 2010-08-30

History

The patient is a 41-year-old male presenting status post-motor vehicle collision.

Findings

AP view of the chest demonstrated a curvilinear shadow arising from the apex of the right lung and terminating in a "tear drop" shadow formed by the azygos vein.

Diagnosis

Azygos lobe

Discussion

The azygos lobe is a normal variant, which occurs in approximately 0.4% of the population. It forms when the azygos vein fails to migrate over the apex of the right lung and instead courses through the right upper lobe dragging along with it the parietal and visceral pleura, forming the azygos fissure. The azygos fissure is a curvilinear line, which extends from the right tracheobronchial angle to the apex of the right lung. The azygos vein lies within the fissure and appears on plain film as a characteristic "tear drop" at the inferior margin of the azygos fissure.

References

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