August 9, 2009

Azygos Fissure

Azygos Fissure
  • Normal variant, found in 1% of anatomic specimen and about 0.4% of chest radiographs
  • Right posterior cardinal vein (precursor of azygos vein) fails to migrate over lung apex, instead penetrating the lung and carrying pleural layers with it.
  • Two folds of parietal and visceral pleural layers create a "fissure"
  • Enclosed lung is a part of apical or posterior segment of the right upper lobe

  • Fine, convex line crosses the apex of the right lung.
  • Azygos vein visible in the lowermost portion of the fissure "teardrop" shape.
  • Absence of azygos vein at the right tracheobronchial angle.

Mimics of Azygos Fissure
  • Scars
  • Walls of bullae
  • Displaced fissures
  • Supernumerary fissures

Mata J, Caceres J, Alegret X, Coscojuela P, De Marcos JA. Imaging of the azygos lobe: normal anatomy and variations. AJR 1991;156:931-937.

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