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.
AnatomyThe 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.
May-Thurner Syndrome- This condition is caused by compression of the left common iliac vein against the lumbar vertebrae under the proximal section of the aneurysmal or tortous left common iliac artery, which may occur with or without a deep vein thrombosis. The pulsations of the artery may damage the endothelium of the left common iliac vein and result in spur formation. This predisposes to deep vein thrombosis formation. Diagnosis is made by CT scan, and treatment involves stenting and thrombolysis. There are other variants of May-Thurner, sometimes left common iliac vein passes between iliopsoas muscle and spine which may cause venous compression. The left common iliac vein may be compressed by left common iliac artery due to high bifurcation of aorta or left sided inferior vena cava.
Transposition of the Inferior vena cava- In some patients the inferior vena cava may lie to the left side of the abdominal aorta instead of the right. This is an important variation to be aware of in diagnostic procedures involving the vessel e.g. abdominal aortic aneurysm repair, inferior vena cava placement filter, nephrectomy and portosystemic shunt placement.
Inferior vena cava filter- If someone had recurrent deep vein thrombosis and is at risk of recurrent pulmonary embolism (or is non compliant with anticoagulant medication) a small filter can be passed through the femoral vein, through the common iliac vein and into the infrarenal inferior vena cava through an image guided procedure. This means that any ascending emboli from the legs will not reach the heart, and go onto the lungs. This is a lifesaving procedure and the filter is usually left in place for a few weeks or months.
- The common iliac vein is formed by the unification of the external and internal iliac vein
- The two common iliac veins unite to form the inferior vena cava, anterior to the sacroiliac joints at vertebral level L5
- The femoral vein is renamed the external iliac vein once it passes the inguinal ligament
- The internal iliac vein drains the pelvic viscera and gluteal region
- The common iliac veins have a few tributaries (right lumbar vein on the right, and left lumbar vein and median sacral veins on the left)
- The inferior vena cava passes through the diaphragm at vertebral level T8, and empties into the right atrium at vertebral level T9