Human Embryology and Teratology
Teaching text 7: Blood vessels and circulation 26: Malformations and anomalies 4
In the region of the inferior vena cava
Double inferior vena cava results from the persistence of the left sacrocardinal vein.
If the inferior vena cava is missing, the subcardinal vein ends in the supracardinal vein instead of the liver. Blood then flows from the renal segment of the inferior vena cava into the right atrium via the azygos vein.