<P> Rarely, the inferior vena cava may vary in its size and position . In transposition of the great arteries the inferior vena cava may lie on the left . It may be replaced by two vessels beneath the level of the renal veins . </P> <P> The inferior vena cava is a vein . It carries deoxygenated blood from the lower half of the body to the right atrium of the heart . </P> <P> The corresponding vein that carries deoxygenated blood from the upper half of the body is the superior vena cava . </P> <P> Health problems attributed to the IVC are most often associated with it being compressed (ruptures are rare because it has a low intraluminal pressure). Typical sources of external pressure are an enlarged aorta (abdominal aortic aneurysm), the gravid uterus (aortocaval compression syndrome) and abdominal maligancies, such as colorectal cancer, renal cell carcinoma and ovarian cancer . Since the inferior vena cava is primarily a right - sided structure, unconscious pregnant women should be turned on to their left side (the recovery position), to relieve pressure on it and facilitate venous return ((citation needed)). In rare cases, straining associated with defecation can lead to restricted blood flow through the IVC and result in syncope (fainting). </P>

What is the function of the super vena cava