The azygos venous system has developed from the postcardinal veins of the embryo, and small parts persist only at the commencement of the azygos vein. Complex embryological development of these veins is a major cause for many possible variations of the azygos system.

The present study was done in the Department of Anatomy, Government Medical College, Amritsar, on a male cadaver aged about 50 years. The thoracic cavity was opened to dissect the azygos system of veins.

The system showed the persistent cranial part of the posterior cardinal vein. This led to the formation of a well-developed venous channel on the left side of the aortic arch and the thoracic aorta. This channel drained the 2nd to 10th left posterior intercostal veins and drained itself into the left brachiocephalic vein (LBV) after crossing the arch of aorta vertically on its right. There was no transvertebral communication between this channel and azygos vein on the right side. The hemiazygos vein (HAV) on the left side was normally formed and immediately drained into the azygos vein by turning to the left. The azygos vein on the right side was also normal.

The presence of such persistent embryological remnant, its position, and approximation to the structures near the arch of aorta should be taken into account to avoid radiological misdiagnosis and surgical complications.

Sehmi S. Prominent Accessory Hemiazygos Vein representing Persistence of Cranial Portion of Posterior Cardinal Vein: Embryological Variant. Curr Trends Diagn Treat 2017;1(1):40-41.