What is an azygos lobe fissure?
An azygos lobe is a normal variant that develops when a laterally displaced azygos vein creates a deep pleural fissure into the apical segment of the right upper lobe during embryological development.
Is azygos fissure normal?
The azygos vein, located at the bottom of the fissure, is visible as a teardrop-shaped opacity [2]. The incidence of this normal variant is estimated between 0.4% and 1.2% [2; 4]. Accessory pulmonary fissures, including the azygos fissure, are known to affect up to 50% of the population.
What causes an azygos lobe?
The azygos lobe is formed when the right posterior cardinal vein, which is one of the precursors of the azygos vein penetrates the right lung apex, rather than migrating over it. The cardinal vein carries both pleural layers with it, resulting in entrapment of a portion of the right upper lobe.
Where is the azygos fissure located?
right lung
It is typically located in the apicomedial portion of the right lung, separated from the rest of the right upper lobe by a visible fissure, termed an azygous fissure. The fissure can be identified as a fine, convex line on a chest radiograph in the para mediastinal portion of the right lung.
How azygos lobe is formed?
An azygos lobe forms when the right posterior cardinal vein, one of the precursors of the azygos vein, fails to slide medially over the apex of the lung and instead penetrates it, carrying with it two pleural layers that invaginate into the superior portion of the right upper lobe 2.
Where is the azygos lobe on a chest radiograph?
Radiographic features. Plain radiograph. The azygos lobe is usually well seen on the chest radiograph, where it is limited by the azygos fissure, a fine, convex (relative to the mediastinum) line that crosses the apex of the right lung.
How does the azygos vein form in the lung?
An azygos lobe forms when the right posterior cardinal vein, one of the precursors of the azygos vein, fails to migrate over the apex of the lung and penetrates it instead, carrying along two pleural layers that invaginates into the upper portion of the right upper lobe 2.
How is the azygos lobe related to thoracotomy?
The lobe potentially impedes an extrapleural approach to the esophagus via thoracotomy and increases the risk of neurovascular damage in thoracoscopic procedures, especially as the phrenic nerve may become trapped in the fissure 7 . Scarring, bullae, and displacement of fissures can all mimic an azygos fissure on chest radiographs 5 .
How does the azygos lobe affect the esophagus?
While the azygos lobe itself is thought to not inherently cause pathology, there are surgical considerations. The lobe potentially impedes an extrapleural approach to the esophagus via thoracotomy and increases the risk of neurovascular damage in thoracoscopic procedures, especially as the phrenic nerve may become trapped in the fissure 7.
