The blood supply to the body arises from the aorta, the main outflow of the left ventricle of the heart. The abdominal aorta gives rise to two common iliac arteries at its termination, which then further divide into the external and internal iliac arteries. In this article we will discuss the anatomy and clinical relevance of the common iliac artery. We will also conclude with a summary and some review questions to test the reader’s understanding of the article content.
The abdominal aorta divides at the level of the fourth vertebral body, and forms the two common iliac arteries. The common iliac arteries run laterally, and divide into the external and internal iliac arteries anterior to the sacroiliac joints. The internal iliac descends into the pelvis to supply the sphincters, reproductive organs and pelvic viscera. The external iliac will continue to run inferiorly, and pass deep to the inguinal ligament. At this point the artery is renamed as the femoral artery, which goes on to supply the lower limb. As the common iliac artery descends, it runs along the medial border of the psoas major muscle. They have peritoneum in front, and is crossed near their bifurcation by the ureter and spermatic nerves and vessels. The arteries are accompanied by the common iliac veins along their course which lie posterior. The right common iliac is slightly longer than left, the average length of common iliac arteries is 2.5 inches.
External Iliac Artery
The external iliac artery arises from the division of the common iliac artery, anterior to the sacroiliac joints. The external iliac artery then continues to pass under the inguinal ligament and is renamed the femoral artery once it emerges. It runs medial to the femoral nerve and lateral to the common iliac vein.
Inferior epigastric artery- (Within the pelvis branch) - This branch passes superiorly, to anastomose with the superior epigastric (a branch of the internal thoracic/mammary artery).
Deep circumflex iliac artery- (Within the pelvis branch) - This branch passes laterally and runs along the iliac crest of the hipbone. The artery arises from the external iliac artery opposite the origin of the inferior epigastric artery. The artery passed upwards, behind the inguinal ligament, and to the anterior superior iliac spine. Here it anastomoses with the ascending branch of the lateral femoral circumflex artery.
Femoral artery- This branch continues down into the inguinal region as a continuation of external iliac, and passes underneath the inguinal ligament. From the anterior aspect of the proximal part of the femoral artery arise the superficial epigastric artery, superficial (and sometimes the deep) circumflex iliac arteries, and the superficial and deep external pudendal arteries. It divides into the profunda femoris, and the superficial femoral artery. The profunda femoris is the blood supply to the muscles of the thigh. Major branches it gives are medial and lateral circumflex femoral arteries. The superficial femoral artery continues down the leg, and passes through Hunter’s/subsartorial canal. After it emerges from the canal, it is renamed as the popliteal artery. The popliteal artery then divides into the anterior and posterior tibial arteries. The anterior tibial artery supplies the anterior compartment of the leg, and the posterior tibial supplies the posterior compartment of the leg. The posterior tibial artery passes behind the medial malleolus, and divides into the medial and lateral plantar arteries, which supply the foot. The fibular artery is a branch of the posterior tibial artery, and supplies the lateral compartment of the leg.
Internal iliac Artery
The internal iliac artery arises from the division of the common iliac artery. The vessel runs posterior to the ureter in its upper section, posterior to the internal iliac vein along its entire course, posterior to the lumbosacral trunk as it passes the sacral foramina. It is separated from the psoas major muscle by the internal iliac vein.
Posterior trunk branches
Iliolumbar artery- This artery is the first branch of the posterior trunk of the internal iliac artery. The artery turns superiorly, as it runs posterior to the obturator nerve, external iliac artery and vein. It next passes to the medial border of the psoas major muscle, where it bifurcates into the lumbar and iliac branches. The lumbar branch supplies quadratus lumborum, psoas major and sends a small spinal branch that passes through the intervertebral foramen between the L5 vertebra and the sacrum. It supplies the cauda equina. The iliac branch supplies the iliacus muscle, and anastomoses with the obturator artery and sends branches to the gluteal and abdominal regions.
Lateral sacral artery- This artery is a branch of the posterior trunk of the internal iliac artery. There is usually a superior and inferior artery. The superior artery anastomoses with the middle sacral artery, which then passes into the first or second anterior sacral foramen. Here it sends branches to the sacral canal contents, and passes through the sacral cavity to the posterior opening, where it sends branches to the skin and posterior surface of the sacrum.
The inferior artery crosses the sacral nerves and piriformis muscle, and descends anterior to the sacrum. The artery anastomoses with the middle sacral and lateral sacral artery of the opposing side. The artery gives off numerous branches that supply the sacral canal contents and like the superior branch, supply the dorsum of the sacrum and skin over the region.
Superior gluteal artery- This is the largest branch of the internal iliac artery. It is in fact a direct continuation of the posterior division of the artery. The artery is relatively short, and passes posteriorly. It runs between the lumbosacral trunk and the first sacral nerve. It emerges from the pelvis by leaving via the greater sciatic foramen, above the piriformis. At this point the artery divides into a superficial and a deep branch. The artery provides blood to the piriformis iliacus and obturator internus muscles.
The superficial branch of the artery immediately enters the deep section of the gluteus maximus muscle, and then further divides into a number of smaller branches. These branches supply the gluteus maximus muscle as well as anastomosing with the inferior gluteal artery. Some of these smaller branches perforate the tendinous origin of gluteus maximus from the sacrum, and anastomose with the lateral sacral arteries.
The deep branch will run beneath the gluteus medius muscle and immediately bifurcates further. The inferior division of the deep branch runs diagonally to reach the greater trochanter of the femur, which emerges from the superolateral surface of the femoral shaft, and is the insertion site of the short external rotators of the hip joint. The artery then gives off a number of gluteal branches, which join the lateral femoral circumflex artery. The superior division will form the continuation of the vessel. It runs to the anterior superior iliac spine, by passing along the superior border of gluteus minimus, At this point the artery anastomoses with the deep iliac circumflex artery, as well as the ascending branch of the lateral femoral circumflex artery.
Anterior trunk branches
Obturator artery- This branch of the internal iliac artery will run forwards and downwards, in close contact with the lateral wall of the pelvis.
It will eventually reach the obturator foramen, and leaves the pelvis cavity by passing through the obturator canal. It then further divides into an anterior and posterior branch.
Inferior gluteal artery- The inferior gluteal artery is a the larger terminal branch from the anterior trunk of the internal iliac artery. It supplies the posterior thigh as well as the buttock. The artery runs on the anterior surface of the piriformis muscle and sacral plexus, and leaves the pelvis by passing between the piriformis and coccygeus muscles.
Umbilical artery- This is functional during foetal life, and runs into the umbilical cord. The arteries carry deoxygenated blood from the foetus to the placenta. Part of it regresses after birth, and becomes the medial umbilical ligament. The artery may gives rise to the superior vesical arteries, and a portion of the artery remains as a branch of the internal iliac artery.
Uterine artery- This artery arises from the anterior division of the internal iliac artery. The artery runs above the ureter, and runs in the cardinal ligament. It passes through the parametrium of the broad ligament of the uterus, and frequently forms an anastomosis with the ovarian artery.
Vaginal artery- This artery arises from the internal iliac artery, and supplies the vagina in females. It is regarded by some as the inferior vesical artery in males., and arises from the uterine artery in some.
Inferior vesical artery- This artery supplies the lower part of the bladder. It is a branch of the anterior division of the internal iliac artery. It also supplies the fundus of the bladder. It supplies the seminal vesicles and prostate in males. Some anatomists regard the vaginal artery to be the female homologue of the inferior vesical artery.
Middle rectal artery- This artery supplies the middle part of the rectum, and proceeds in the pararectal fascia to anastomose with the branches of superior rectal artery and inferior rectal artery. It also gives branches to the prostate and the seminal vesicles.
Internal pudendal artery- This is the branch of the anterior division of the internal iliac artery arises just below the origin of obturator artery. The artery gives rise to branches that supply the external genitalia, and also gives rise to the inferior rectal artery. The artery leaves the greater sciatic foramen between the piriformis and coccygeus muscle, and winds around the sacrospinous ligament. It then re-enters the pelvis via the lesser sciatic foramen. It passes through the pudendal canal in the lateral wall of ischioanal fossa. On its exit it divides into two terminal branches deep and dorsal arteries of penis (clitoris).
Common Iliac artery aneurysms- Aneurysms of the common iliac artery do occasionally occur. 10-20% of abdominal aortic aneurysms is associated with aneurysm of the common iliac artery. They are usually asymptomatic, but may present with hydronephrosis (due to ureteric blockage), neurological symptoms (sciatic nerve compression). If they rupture then symptoms include shock, and abdominal pain.
Surgical relevance- The ureters run underneath the uterine arteries (hence the saying, ‘water under the bridge’). It can be damaged in operation to the uterus such as hysterectomy.
Severe haemorrhage in the lower limb can be reduced by ligation of the internal iliac artery while surgical repair takes place. The pelvis also has significant collateral circulation which is able to ensure an adequate blood supply even in the event of vascular compromise.
EVAR (endovascular aneurysm repair)- This is a procedure for the repair of abdominal aortic aneurysm, it involves the insertion of a trouser leg graft into the femoral artery, and the graft will expand and close any leakage in the abdominal aorta. This minimally invasive approach reduces post-procedure morbidity, but leads to higher rates of some complications e.g. aortoenteric fistula.