MeSH definition : A vein which arises from the right ascending lumbar vein or the vena cava, enters
the thorax through the aortic orifice in the diaphragm, and terminates in the superior
vena cava.;
A vein which arises from the right ascending lumbar vein or the vena cava, enters
the thorax through the aortic orifice in the diaphragm, and terminates in the superior
vena cava.
http://www.orpha.net/consor/cgi-bin/OC_Exp.php?Lng=FR&Expert=99121 2011 France scientific and technical information azygos vein vena cava, inferior