The common iliac vein is formed by the unification of the internal and external iliac veins The external iliac vein drains the lower limb, and the internal iliac vein drains the gluteal region and pelvic viscera. The unification of the two common iliac vein forms the inferior vena cava. In this article we will discuss the basic venous anatomy of the lower limb in order to frame the common iliac vein in a larger anatomical context. We will also discuss the regional anatomical relations of the left and right common iliac veins, and also the clinical relevance of the common iliac vein as well as its tributaries. We will also conclude with a summary and some review questions to test the reader’s understanding of the article content.
The popliteal vein is the middle structure of the popliteal fossa (deep to sciatic nerve, superficial to popliteal artery), and drains the short saphenous vein (drains the superficial lateral leg compartment), the anterior tibial (drains the anterior leg compartment), posterior tibial (drains the posterior leg compartment) and fibular veins (drains the lateral leg compartment). The popliteal vein becomes the femoral vein when it passes through the adductor hiatus/hunter’s canal along with the artery and the saphenous nerve (a branch of the femoral nerve). Once the femoral vein passes the inguinal ligament, it is renamed the external iliac vein. The external iliac vein drains the inferior epigastric vein, deep circumflex iliac vein and also the pubic vein. The common iliac vein is formed by the unification of the internal (drains the pelvic organs) and external iliac veins just in front of the sacroiliac joint. The internal iliac vein drains all of the veins of the pelvic cavity and some of the gluteal region. The extra pelvic veins include the superior and inferior gluteal veins, the obturator (drains the lateral pelvis wall) and internal pudendal veins (drains the pelvis). The pelvis veins include the lateral sacral, median sacral, uterine, vaginal and vesical veins. The latter four veins drain both the presacral venous plexus and the visceral venous plexuses i.e. the prostatic, uterine, rectal and vaginal plexuses.
The common iliac veins unite with the common iliac vein of the contralateral side slightly at the right side of vertebral level L5. They form the inferior vena cava. Both the internal and common iliac veins are valveless. The external iliac vein may have a single valve. The right common iliac vein begins medial to the right common iliac artery but as it ascends it runs posterior to the artery, this vein is more shorter and vertical. Right obturator nerve is in its posterior relation. The left common iliac vein runs medial to the left common iliac artery then also becomes posterior. Left common iliac is longer and more oblique. This vein has attachment of sigmoid mesocolon and superior rectal vessel in its anterior relations.
Both of the veins drain iliolumbar and lateral sacral vein (sometimes). The left common iliac vein also receive median sacral vein. The inferior vena cava then ascends to the right of the vertebral column and passes through the diaphragm at vertebral level T8-T9. After approximately 2.5cm of length in the thoracic cavity, the inferior vena cava then drains into the the inferoposterior part of right atrium.