Variation of hemiazygos vein with absence of accessory hemiazygos vein- a dissection study

Hemiazygos vein and Accessory hemiazygos vein lie on the left side in the posterior mediastinum of thorax and are the counterpart of azygos vein on right side. During routine cadaveric dissection of thoracic region in an adult male, we found an abnormal venous channel which was single and was lying on the left side of the vertebral column. It received tributaries from superior intercostal vein and posterior intercostal veins. We found this abnormal venous channel draining directly into left brachiocephalic vein in contrast to its usual drainage into azygos vein. Hence this can be considered as abnormal venous channel and variant of hemiazygos vein and accessory hemiazygos vein. The azygos and hemiazygos venous system is commonly encountered during surgical intervention performed on posterior thoracic wall. This case report provides a new data of potential clinical significance.