Anatomy@Edinburgh

Anatomical variation of the azygos venous system and its clinical implications

Former MSc Human Anatomy students Christina Loukopoulou, Zaid Osama Alturkistani, Mohammed Algarni, Blessings Dickxie Kachere and their supervisor Abduelmenem Alashkham have presented their work at British Association of Clinical Anatomists conference in which neurogenic tumours, infectious spondylitis and spinal meningoceles are some of the most frequently occurring posterior mediastinal lesions.

Due to its location and proximity to the spinal column, knowledge of variations involving the azygos venous system is indispensable in surgical procedures such as resection of neurogenic posterior mediastinal tumours, posterior meningocele repair as well as cannulation and ligation of the azygos vein during thoracotomy. During routine postgraduate dissection in Anatomy, University of Edinburgh, a 99-year-old female cadaver demonstrated a left- sided azygos vein. It was observed to form directly from the union of the left ascending lumbar and left subcostal veins. The azygos vein ascended ipsilaterally, in between the thoracic aorta and the sympathetic chain. It then crossed the midline, to the right side, at the level of the 5th thoracic vertebra, before ultimately draining into the superior vena cava. With an absent superior hemiazygos vein, two inferior hemiazygos (superior and inferior) veins on the left side were observed: both veins drained into the azygos vein at the level of 9th and 10th thoracic vertebrae respectively. Azygos vein laceration carries a universally poor prognosis, thus awareness of such variations is vital in prohibiting iatrogenic bleeding or radiological misdiagnosis.