External Iliac Vein

The external iliac veins carry oxygen-poor blood from your lower body to your heart. Blood clots can form in your iliac veins, leading to dangerous deep vein thrombosis (DVT) and pulmonary embolisms. The external and internal iliac veins combine to form common iliac veins. These veins join to become the inferior vena cava, your largest vein.


Diagram shows how your external iliac veins connect to the rest of your circulatory system.
Your external iliac veins bring blood from your abdomen and legs back to your heart to get oxygen.

What are the external iliac veins?

The external iliac veins are blood vessels in your pelvis. Your pelvis is the part of your skeletal system between your lower torso (trunk) and legs. It sits just above where your legs and hips connect.

Your external iliac veins send blood that no longer has oxygen from your lower body back to your heart to get oxygen. These veins are a continuation of the femoral veins, major blood vessels in your thighs. They help carry deoxygenated blood from your legs to your heart.


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What are the internal iliac veins?

The internal iliac veins function alongside the external iliac veins. They carry deoxygenated blood from organs in your pelvic area back to your heart. Your internal iliac veins also drain blood from your:

  • Buttocks.
  • External genitals.
  • Inner thigh.
  • Perineum (the area between your anus and your scrotum or vulva).


What is the external iliac vein function?

As part of your body’s circulatory system, the external iliac veins carry blood that’s low in oxygen back to your heart from the:

  • Front of your abdomen and abdominal organs.
  • Lower legs.
  • Pubic region and reproductive organs.


What is blood that’s low in oxygen?

Your circulatory system is made up of arteries, veins and other blood vessels. Most arteries carry blood that has oxygen and nutrients to organs and tissues throughout the body. Oxygenated blood or red blood is rich in oxygen.

After your body uses the oxygen in blood, your veins carry the deoxygenated blood back to your heart. Your heart pumps the blood to the pulmonary arteries in your lungs to get oxygen. You may hear the terms blue blood or oxygen-poor blood to refer to blood that’s low in oxygen.


How do internal and external iliac veins fit into the circulatory system?

Each side of your body has an external and internal iliac vein. These veins are peripheral blood vessels, which means they are far from your heart. Iliac arteries run alongside the iliac veins.

Around your sacroiliac (SI) joint, the pairs of external and internal iliac veins join to form the right and left common iliac veins. The SI joint is where the sacrum (the bottom section of your spine) meets your pelvis.

Higher up, near the fifth vertebra in your spine, the right common iliac vein and left common iliac vein come together to create the inferior vena cava. The inferior vena cava is your body’s largest vein. It carries oxygen-poor blood from your lower body to your heart.


Where are the external iliac veins?

The external iliac veins are in your pelvis. They’re an upward continuation of the femoral veins in your thighs. External iliac veins:

  • Start behind the inguinal ligament, two narrow bands in the pubic area that connect your abdominal muscles to your pelvis.
  • Travel parallel to the iliac arteries, which carry oxygenated blood to your legs, pelvic region and reproductive organs.
  • Run along the top of your pelvis (pelvic brim) toward the sacrum.
  • Cross the kidney ureters and vas deferens (part of the male reproductive system) or ovaries (part of the female reproductive system).
  • Join the internal iliac veins to form the common iliac veins, which create the inferior vena cava.

What veins feed into the external iliac veins?

Several smaller veins send deoxygenated blood to the external iliac veins:

  • Inferior epigastric vein: Drains blood from the front abdominal muscles that sit just above the inguinal ligament.
  • Deep iliac circumflex vein: Crosses the external iliac artery to send blood into the external iliac vein.
  • Pubic vein: Sends blood from the pubic region.

Conditions and Disorders

What conditions affect the external iliac veins?

The following conditions can affect external iliac veins:

  • Deep vein thrombosis (DVT): One or more blood clots form in a vein deep in your legs. The clot may block blood flow through the vein. A clot that stays in your leg is a thrombus. While a thrombus may not be life-threatening, you need treatment to break up the clot and keep it from becoming an embolus (a clot that travels in the bloodstream).
  • Pulmonary embolisms: A DVT breaks free from a vein in your leg and travels toward your lungs. The clot (embolus) lodges in your pulmonary arteries, which carry deoxygenated blood to the lungs. Your lungs receive low amounts of blood and oxygen, while blood pressure in your pulmonary arteries increases. Pulmonary embolisms can damage the heart and lungs. This life-threatening problem requires immediate medical care.
  • Chronic venous insufficiency (CVI): Healthy leg veins have valves that help deoxygenated blood flow back to your heart. Damaged valves allow blood to leak backward. Blood collects in your lower legs, causing swelling and pressure in your legs. DVTs, high blood pressure, pelvic tumors and vascular malformations can cause CVI.
  • May-Thurner syndrome: This syndrome is also called iliac vein compression syndrome. It occurs when the right iliac artery presses the left iliac vein against your The compressed vein can’t carry blood back to your heart as it should. Blood can pool causing swelling and, in some cases, DVTs form.


How can I protect my external iliac veins?

These actions can keep your external iliac veins healthy while lowering your risk of blood clots:

  • Avoid long periods of standing or sitting, which can allow clots to form. Try to walk or move at least once every hour, and strive to be physically active most days of the week.
  • Eat a heart-healthy diet that’s low in fat and cholesterol to maintain a healthy weight.
  • Find healthy ways to manage stress, like meditation or walking with a friend.
  • Manage conditions that damage blood vessels, like diabetes, high blood pressure and high cholesterol.
  • Quit smoking and using tobacco products. Tobacco use damages arteries and veins.
  • Wear compression stockings (if recommended by your healthcare provider) to prevent blood clots and blood pooling in your legs.

Additional Common Questions

When should I talk to a doctor?

You should call your healthcare provider if you experience:

A note from Cleveland Clinic

The external iliac veins play a critical role in sending oxygen-poor blood from your lower extremities to your heart. These veins connect to the femoral and internal iliac veins to form the inferior vena cava, the body’s largest vein. Blood clots can form in veins deep in your legs, increasing your risk for potentially life-threatening problems like deep vein thrombosis and pulmonary embolisms. Getting quick care for symptoms of vein problems can safeguard your health.

Medically Reviewed

Last reviewed on 03/15/2022.

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