40 - Gross Dissection of an Anatomical Variant of the Azygos Venous System

Poster Board Number: 40
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Abstract Body : Objective: Identifying the variations in the pathway of azygos and hemiazygos vein and its importance.

The azygos system of veins has many anatomical variations that can impact mediastinal and vascular interventions. Thus, radiological reports on these are of great clinical value. To our knowledge, this study is among the first to present a high-quality cadaveric dissection of a rare anatomical variant to supplement previously published radiologic studies. The azygos venous system consists of the azygos vein, hemiazygos vein (HAV) and the accessory hemiazygos vein (AHAV), which develop from the last portion of the posterior cardinal veins. The normal anatomical configuration includes drainage of the posterior intercostal veins, vertebrae, esophageal, HAV and AHAV to an unpaired right-side azygos vein at the level of the eighth and/or ninth thoracic vertebra. We document here a direct connection of the HAV to the AHAV with AHAV draining into the left brachiocephalic vein and a single azygos-hemiazygos anastomosis. The reported incidence of AHAV draining directly into the left brachiocephalic vein is 1-2% . It is important to note the variations of the azygos system to avoid confusion with a potential pathology such as mediastinal masses. Understanding of the rare variant reported here could be useful in prevention of iatrogenic bleeding from misplacement of venous catheters and help facilitate radiological diagnosis in the incidence of venous clot formation.