AZYGOS VEINS VARIATIONS IN VIEW OF THEIR DEVELOPMENTAL BASIS: CASE REPORT.

Introduction:- The azygos system of veins anatomical variations are usually explained on the basis of their embryological development. These variations are deserves to be highlighted and reported. Because, for its clinical importance as it acts as a collateral circulation and an alternative pathway in the case of vena caval obstructions, and it is essential for radiographic imaging and avoiding posterior mediastinum surgical complications for optimal patient 's outcome. Material and method:- A dissection of posterior mediastinum of the adult two male cadavers in our anatomy department, showed multiple abnormalities of the azygos venous system Result:- In case (1), the azygos vein, formed by the right subcostal vein only, with an absence of the right ascending lumbar vein. The hemiazygos vein was found to be formed by the union between the left subcostal and the left eleventh posterior intercostal veins. While, The 6th and 7th left posterior intercostal veins conjugated and formed a single root which in turn received the accessory hemiazygos vein that appear to be formed by the 3rd, 4th and 5th left posterior intercostal veins. In case (2), the left azygos venous line was ill defined and the lower eight left posterior intercostal veins were opening independently into the azygos vein by three venous connections. We discussed these variations in view of their embryological developmental basis. Conclusion:- Obstruction of the cardinal veins normal developmental manner can result in azygos veins abnormalities.