Common iliac vein

The common iliac vein is a major venous trunk in domestic mammals that serves to return deoxygenated blood from the pelvic limbs, pelvic cavity, and associated structures to the caudal vena cava. It is formed by the confluence of the external iliac vein and the internal iliac vein on each side of the body.

Species-Specific Anatomy

Dog and Cat

• In the dog and cat, the common iliac veins are relatively short.

• Formation: Each common iliac vein is formed by the union of:

  • External iliac vein (drains the pelvic limb)

  • Internal iliac vein (drains pelvic viscera and part of the perineum)

• These veins unite near the level of the lumbosacral junction to form the caudal vena cava.

• Tributaries may include the median sacral vein, which often drains into the left common iliac vein or directly into the caudal vena cava.

Ruminants (Cattle, Sheep, Goat)

• The anatomy is similar to that in dogs, but the common iliac veins are proportionally longer due to the larger size of the pelvis.

• The internal iliac vein is particularly well-developed because of the extensive venous return from the ruminoreticulum and pelvic viscera.

• Additional tributaries include iliolumbar veins, lumbar veins, and possibly the deep circumflex iliac vein.

Horse

• In the horse, the common iliac vein is longer and more prominent than in small animals.

• It lies ventral to the common iliac artery.

• The left and right common iliac veins join cranial to the pelvic inlet to form the caudal vena cava.

• The deep circumflex iliac vein and lumbar veins are important tributaries.

Pig

• The pig shows a variation in which the common iliac vein may not be distinctly formed, and the internal and external iliac veins drain directly into the caudal vena cava.

• There may be asymmetry between the left and right venous structures, especially with the median sacral vein, which often drains into the left side.

Position and Relations

• The common iliac veins are located in the retroperitoneal space, dorsal to the peritoneum and ventral to the lumbar vertebrae.

• They run alongside the common iliac arteries, but lie medial and slightly dorsal to them.

• They are closely associated with the ureters, sympathetic chain, and lymphatic vessels of the pelvis.