Internal iliac vein (hypogastric vein)
The internal iliac vein starts at the upper region of the greater sciatic foramen, a large gap in the bone of the pelvis on each side of the sacrum. It continues behind the internal iliac artery and reaches the pelvis. From there it meets the external iliac vein, and together they become the common iliac vein. Eventually this vein will flow into the inferior vena cava, which is the largest vein in the human body. These veins drain blood away from the reproductive, urinary, and digestive organs.
The internal iliac vein and its branches is are part of several venous plexuses, which are interconnected networks of veins. These include the rectal, vesical, prostatic (in males), vaginal (in females), and uterine (in females) venous plexuses.
In a male, this vein will be in the region of the prostate gland. In a female, it will be in the uterine and vaginal areas.