Vessel
Common iliac veins
Pelvic and limb outflow converging into the cava
High-yield
Common iliac veins usually unite near L5. The artery-over-vein crossing on the left is the anatomical basis of a common iliac compression pattern.
Overview
Internal and external iliac veins unite to form each common iliac vein. The left takes a longer, more oblique route toward the right-sided cava and passes beneath the right common iliac artery before the two veins meet.
Reference facts
- Origin
- Union of internal and external iliac veins near each sacroiliac region.
- Course
- Ascend toward the caval confluence; the left crosses obliquely behind the right common iliac artery.
- Branches
- May receive iliolumbar and sacral tributaries; median-sacral drainage commonly reaches the left side.
- Supplies
- Return blood from pelvic, perineal and lower-limb territories.
- Drains to
- Usually unite near L5 to form the inferior vena cava.
Clinical correlation
Compression at this crossing may contribute to left iliac venous obstruction or thrombosis. The anatomical configuration can occur without symptoms; symptomatic obstruction is described as May–Thurner syndrome.
Frequently asked questions
Where do the common iliac veins originate?
The common iliac veins arise from the union of internal and external iliac veins near each sacroiliac region.
What do the common iliac veins supply?
The common iliac veins supply the return blood from pelvic, perineal and lower-limb territories.
Where do the common iliac veins drain to?
Usually unite near L5 to form the inferior vena cava.
What are the branches of the common iliac veins?
May receive iliolumbar and sacral tributaries; median-sacral drainage commonly reaches the left side.