The common iliac vein (created by the union of the internal and external iliac veins) forms in the abdomen, at the level of the fifth lumbar vertebrae. It divides into two branches. The internal iliac vein drains blood from the visceral organs in the pelvic region. The external iliac connects to the femoral veins. The internal iliac vein may double or lay lateral to the external iliac vein. Both veins join together to form the inferior vena cava.

The vein receives blood from the reproductive organs. The veins form networks known as plexuses. Plexuses are located in the anus, prostate glands, and urinary bladder in males. Plexuses are also found in the vagina and the uterus in females.

The external iliac vein is located in the lower leg. The vein begins behind the inguinal ligament. The vein passes through the pelvis and ends opposite the sacroiliac articulation. The external iliac vein receives three veins: the pubic, inferior epigastric, and deep iliac circumflex veins. The internal iliac vein is the hypogastric vein. At the brim of the pelvis, it joins the external iliac vein to form the common iliac vein.