Imaging Case of the Week 51

This chest x-ray is from a 55 year old man who presented to the ED with dyspnoea. Largely, it looks normal. However, there is a subtle anatomical variant visible on the x-ray. Can you spot it?

chest  x-ray

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[peekaboo_link name=”Answer”]Answer[/peekaboo_link] [peekaboo_content name=”Answer”]

There is an azygous lobe, a developmental anomaly seen in about 1% of the general population. It is a small accessory lobe found on the right lung apical area.

The azygous fissure is visible as a fine convex line which separates the lobe from the rest of the upper lobe. The thickened lower part of the fissure contains the azygous vein.

Azygous lobe

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Azygous lobe and fissure

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It is of no clinical significance. However, the end-on appearance of the azygous vein can sometimes be confused for a pulmonary nodule.