what does the external iliac vein drain
1 Common iliac vein, formed by the external and internal iliac veins, drains into the inferior vena cava. 2  Deep circumflex iliac vein, formed by the union of the venae comitantes of the deep iliac circumflex artery, and joins the external iliac vein. Deep circumflex iliac vein, formed by the union of the venae comitantes of the deep iliac circumflex artery, and joins the external iliac vein. 2  External iliac vein, terminates at the common iliac vein, drains the femoral vein. 3  Internal iliac vein, terminates at the common iliac vein, drains pelvic organs and perineum.