A Variation in the Formation of the Azygos Vein and a Genesis of the Hemiazygos Vein and the Accessory Hemiazygos Vein

The variations were detected in the azygos vein system during dissection of the posterior thoracic Wall of a 62-year-old male cadaver. The hemiazygos vein and the accessory hemiazygos vein were underdeveloped. The right and the left ascending lumbar veins united and formed the azygos vein at the level of the Th11 vertebral body. The azygos vein was coursed on the midline with the thoracic duct and ended in the superior vena cava at the level of the Th4 vertebra. On the left side of the vertebral column; the veins from 3rd to 10th intercostals spaces united and formed three trunks (superior, middle and inferior) which drained into the azygos vein separately. Knowledge of variations in the azygos vein system is important in mediastinal surgery and also in the interpretation of radiographs related with this region.