An azygos fissure is a normal anatomical variant seen in the right lung.
It is formed when the azygos vein deviates laterally from its usual position and passes through the upper lobe of the right lung, dragging a layer of visceral pleura with it.
This results in the creation of an accessory fissure, separating a small portion of the lung (called the azygos lobe) from the rest of the right upper lobe.
The azygos fissure is not a true fissure anatomically, as it is formed by four pleural layers: two parietal and two visceral.
Radiological Characteristics:
On Chest X-ray (CXR):
Appears as a thin, curvilinear line in the upper right lung field.
Typically seen as a convex line running medially toward the hilum, with a small nodular opacity (the azygos vein) at its medial end.
On Chest CT:
Clearly shows the azygos vein within the fissure, surrounded by pleural layers.
Confirms the presence of the azygos lobe and its anatomical relationships.
Differentiates the azygos fissure from pathological fissures or other abnormalities.
Common Diseases and Conditions Associated:
Typically an incidental finding with no clinical significance.
Rarely associated with:
Misinterpretation as a pathological lesion (e.g., pleural thickening or mass).
Technical challenges in thoracic surgery, as the azygos vein’s location may vary.
Increased complexity in procedures like lung biopsies or lobectomies.
Clinical Relevance:
The azygos fissure does not represent a disease but rather a variant of normal anatomy.
Recognition on imaging is important to avoid misdiagnosis and guide surgical planning when necessary.
