Azygos fissure
- An azygos fissure is seen on approximately 1-2% of chest X-rays - autopsy studies suggest they are more common
- The azygos vein, which is lined by visceral and parietal pleura, lies in the base of the fissure
- Medially there is a small connection of the 'azygos lobe' with the rest of the upper lobe
- An azygos fissure has a tadpole shape, the azygos vein itself forming the head of the tadpole
- Because the azygos vein is a right-sided structure, this accessory fissure is only ever seen on the right side of the chest