BOF: 40
A 46-year-old male presents with chest pain. He has a chest
x-ray and the radiology registrar who reports on it tells you that the only
abnormality he can see on it is a “reverse comma sign” in the right apex. Your
house office asks you what this is and your reply is that the reverse comma is
caused by failure of migration of the azygos vein during development and it is
made up of:
a)
Fibrous tissue and the azygos vein
b)
Parietal pleura and the azygos vein
c)
Visceral pleura and the azygos vein
d)
Visceral and parietal pleura and the azygos vein
e)
Azygos vein
Answer:
d)
The patient has an azygos lobe, which is a normal variant
that may occur in less than 5 % of the population. It is caused by failure of
migration of the azygos vein over the apex of the lung during foetal life. It
courses through the lung instead and drags down two layers of parietal and two
layers of visceral pleura with the vein lying at the inferior aspect. The four
layers of pleura make up the azygos fissure and this together with the vein at
its inferior aspect give “the reverse coma sign”. The vein seen end on may
sometimes be mistaken for an upper lobe pulmonary mass.
Last Updated: 22/04/06
