What is Dr. Zubair Khalid's research focus?

Dr. Zubair Khalid specializes in molecular virology, mRNA vaccine development, and computational biology, with a focus on avian pathogens like IBDV and Avian Reovirus.

Where is Dr. Zubair Khalid currently working?

Dr. Zubair Khalid is a Postdoctoral Research Associate at the University of Maryland (UMD), specifically within the Department of Animal and Avian Sciences.

Iliac Artery Anatomy: Common, Internal, and External

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-09-19

The abdominal aorta ends at roughly the L4 vertebral level, where it splits into the right and left common iliac arteries. Each common iliac artery runs about 4 to 5 cm in adults before dividing into two very different vessels: the internal iliac artery, which supplies the pelvic organs, gluteal muscles and perineum, and the external iliac artery, which leaves the pelvis under the inguinal ligament and becomes the femoral artery of the leg.

That single fork explains a lot of clinical medicine. Pelvic surgery, aortic aneurysm repair, catheter angiography and endurance-athlete leg pain all hinge on knowing which branch goes where. This guide walks through the iliac artery anatomy in plain language, compares the internal and external territories, and gives a branch table you can use as a reference.

The Bifurcation of the Abdominal Aorta

The abdominal aorta descends in front of the lumbar vertebral bodies and ends in a terminal bifurcation. In most adults this happens near the lower border of the fourth lumbar vertebra (L4), at the level of the iliac crests and just above the sacral promontory. The two resulting common iliac arteries pass downward and laterally to reach the pelvic brim.

Vertebral levels are averages, not constants. A 2026 case report described a 17-year-old male with a high aortic bifurcation at the inferior margin of L3 and a markedly short left common iliac artery that divided at the superior margin of L4, with the left internal and external iliac arteries then running in close apposition along the front of L4 and L5 [1]. At the other extreme, a dissection of a 98-year-old female donor found congenital absence of the left common iliac artery, with the aorta dividing directly into the right common iliac artery and the left internal and external iliac arteries at the fifth lumbar vertebra [2]. These variants matter because they change the distance a surgeon or interventionalist has to work with.

The relationship between the bifurcation and the sacral promontory has been studied specifically in the context of sacropexy, the suspension of the vaginal apex to the sacrum. That work treats the bifurcation-to-promontory distance as a measurable anatomic variable relevant to safe suture placement [3].

How Long Is a Common Iliac Artery?

A typical adult common iliac artery measures about 4 to 5 cm from the aortic bifurcation to its own division. Length is the variable that most often causes trouble. Short common iliac arteries limit how much landing zone an endovascular stent graft has before it reaches the internal iliac artery origin, and extremely short segments have been managed with salvage hybrid reconstructions that keep pelvic flow open [4]. Longer, more tortuous common iliac arteries create different problems, mainly difficulty tracking devices and a higher chance of stent migration.

The Common Iliac Artery

The common iliac artery is a muscular artery with a modest caliber, and it is usually described as having no major named branches. That textbook statement is close to true but not exact. A 2024 angiographic study of 100 consecutive pelvic angiograms found that branches arose from 38 common iliac arteries in 30 patients, meaning about 19% of common iliac arteries and 30% of patients had at least one detectable branch. Of those branches, 46.5% were classified as normal (small rami to neighboring structures), 48.8% as aberrant (replacing a normal artery) and 4.7% as accessory (supplementing a normal artery). The larger branches participated in supplying the psoas muscle and the ureter, and every patient with an aberrant branch had at least one anomalous vessel capable of feeding a radiculomedullary territory [5].

That last point is the practical one. A vessel most clinicians never think about can be the artery feeding the spinal cord, and losing it during a pelvic procedure can cause cord ischemia.

Where the Common Iliac Artery Divides

Each common iliac artery ends by dividing into the internal iliac artery and the external iliac artery. The division usually occurs at or just below the level of the lumbosacral disc, anterior to the sacroiliac joint. From there the two daughter vessels diverge sharply. The external iliac artery continues anterolaterally along the pelvic brim toward the groin, while the internal iliac artery turns posteromedially and descends into the true pelvis.

The Internal Iliac Artery

The internal iliac artery, historically called the hypogastric artery, is the main blood supply of the pelvis. It is a short trunk, roughly 3 to 4 cm long, that divides almost immediately into an anterior division and a posterior division. A 2025 computed tomography angiography study measured the anterior division at its origin and found a median diameter of 5.76 mm and a median cross-sectional area of 24.77 mm² [6]. A companion study of the posterior division found a median diameter of 6.66 mm and a median cross-sectional area of 34.59 mm² at its origin [7]. Those numbers are useful when planning catheter selection or graft sizing.

The internal iliac artery supplies the pelvic viscera (bladder, rectum, reproductive organs), the gluteal and lateral rotator muscles of the hip, the perineum, the pelvic floor, and part of the bony pelvis and sacrum. It also has a role that surprises many clinicians: branches of the internal iliac artery can feed spinal arteriovenous fistulas, which are easily missed on spinal angiography. In a series of 13 patients with spinal AVFs supplied by internal iliac branches, fistulas ranged from L5 to S4, and 10 of 13 patients (76.9%) achieved immediate occlusion after embolization, though three lesions recurred [8].

Anterior Division Branches

The anterior division of the internal iliac artery (ADIIA) supplies the pelvic organs, perineum and gluteal region [6]. Its named branches include:

Umbilical artery. In the fetus this carries blood to the placenta. After birth the distal portion obliterates into the medial umbilical ligament, but the proximal part stays open and gives rise to the superior vesical arteries that supply the bladder.
Obturator artery. Runs through the obturator canal with the obturator nerve to supply the medial thigh adductors. It has a well-known anastomosis with the medial circumflex femoral artery and the inferior epigastric artery around the obturator foramen.
Inferior vesical artery. Supplies the bladder base, prostate and seminal vesicles in males, and corresponds to the vaginal artery in females.
Middle rectal artery. Supplies the lower rectum and anastomoses with the superior rectal artery (from the inferior mesenteric artery) and the inferior rectal artery (from the internal pudendal artery).
Uterine artery. In females it crosses above the ureter to reach the uterus and anastomoses with the ovarian artery.
Vaginal artery. Supplies the vagina and anastomoses with the uterine and internal pudendal arteries.
Internal pudendal artery. The principal artery of the perineum. It supplies the external genitalia, the perineal muscles and the anal canal, and it anastomoses with the external pudendal arteries.
Inferior gluteal artery. Exits the pelvis below the piriformis muscle to supply the gluteus maximus and the back of the thigh, and anastomoses with the superior gluteal, medial circumflex femoral and perforating arteries.

The 2025 CTA analysis found the internal pudendal artery in 134 of 148 studied anterior divisions (90.5%), making it the most prevalent branch. The umbilical artery was the most common first branch at 48.5%, and the inferior gluteal artery was the most common last branch at 68.4%. The median distance from the anterior division origin to the uterine artery origin was 12.00 mm [6].

Posterior Division Branches

The posterior division of the internal iliac artery (PDIIA) supplies the musculoskeletal framework of the pelvis and the gluteal region [7]. Its named branches include:

Iliolumbar artery. Ascends to supply the iliacus, psoas major and quadratus lumborum, and anastomoses with the lumbar arteries and the deep circumflex iliac artery.
Lateral sacral arteries. Usually two or more, they descend on the sacrum to supply the sacral canal contents and adjacent muscles, and anastomose with the median sacral artery and the iliolumbar artery.
Superior gluteal artery. The largest branch of the internal iliac system. It exits above the piriformis through the greater sciatic foramen to supply the gluteus medius and minimus and the tensor fasciae latae, and it anastomoses with the inferior gluteal and lateral circumflex femoral arteries.

The 2024 CTA study of 75 angiographies found the superior gluteal artery to be the most prevalent posterior division branch, present in 114 of the studied cases (77.03%) [7].

Branch Table: Internal Iliac Artery

Branch	Division	Origin	Territory	Key anastomoses
Umbilical (superior vesical)	Anterior	Proximal anterior division	Bladder, medial umbilical ligament	Vesical branches, obturator
Obturator	Anterior	Anterior division	Medial thigh adductors, obturator canal	Inferior epigastric, medial circumflex femoral
Inferior vesical / vaginal	Anterior	Anterior division	Bladder base, prostate, vagina	Uterine, middle rectal
Middle rectal	Anterior	Anterior division	Lower rectum, anal canal	Superior rectal, inferior rectal
Uterine	Anterior	Anterior division	Uterus, upper vagina	Ovarian, vaginal
Internal pudendal	Anterior	Anterior division	Perineum, external genitalia, anal canal	External pudendal, inferior rectal
Inferior gluteal	Anterior	Anterior division	Gluteus maximus, posterior thigh	Superior gluteal, medial circumflex femoral, perforating
Iliolumbar	Posterior	Posterior division	Iliacus, psoas, quadratus lumborum	Lumbar arteries, deep circumflex iliac
Lateral sacral	Posterior	Posterior division	Sacrum, sacral canal contents	Median sacral, iliolumbar
Superior gluteal	Posterior	Posterior division	Gluteus medius and minimus, tensor fasciae latae	Inferior gluteal, lateral circumflex femoral

The External Iliac Artery

The external iliac artery is the vessel that carries blood out of the pelvis and into the lower limb. It begins at the division of the common iliac artery and runs along the medial border of the psoas major muscle, following the arcuate line of the ilium down to the inguinal ligament. It is larger in caliber than the internal iliac artery and has a more predictable course.

The external iliac artery has only two named branches, both of which arise just above the inguinal ligament:

Inferior epigastric artery. Arises from the anterior surface of the external iliac artery just above the inguinal ligament. It ascends along the posterior rectus sheath and supplies the lower anterior abdominal wall, and it anastomoses with the superior epigastric artery (from the internal thoracic artery) and with the obturator artery through the pubic anastomosis.
Deep circumflex iliac artery. Arises from the lateral surface of the external iliac artery near the inguinal ligament. It runs laterally along the iliac crest and supplies the lower abdominal wall, iliacus muscle and the bone of the iliac crest, and it anastomoses with the iliolumbar and superior gluteal arteries.

From External Iliac to Femoral Artery

The external iliac artery passes beneath the inguinal ligament at the midpoint of the inguinal crease. At that point it is renamed the femoral artery. The name change is not a change in the vessel itself, only a change in its anatomic designation based on the boundary it crosses. The femoral artery then continues down the thigh, where it gives off the profunda femoris (deep femoral) artery and eventually becomes the popliteal artery behind the knee.

That transition zone is where external iliac artery endofibrosis occurs. Endofibrosis is a rare, non-atherosclerotic condition that affects endurance athletes, most often cyclists, and presents as exercise-induced claudication that is frequently misattributed to musculoskeletal or neurologic causes [9][10]. Three reported cases included a 55-year-old male cyclist treated with surgical revascularization for right external iliac stenosis, a 43-year-old female physical education teacher treated with a prosthetic bypass graft for a loop configuration of the external iliac artery, and an amateur triathlete who presented with acute ischemia and required urgent revascularization with an interposition graft. All three resumed their athletic activities [9].

Internal vs External Iliac Territories: A Comparison

The two iliac branches serve almost entirely separate worlds, and that separation is the reason the anatomy matters clinically.

Feature	Internal iliac artery	External iliac artery
Alternative name	Hypogastric artery	None
Direction after division	Posteromedial, into true pelvis	Anterolateral, along pelvic brim
Main divisions	Anterior and posterior	No divisions, just two branches
Named branches	About 10, including umbilical, obturator, internal pudendal, superior and inferior gluteal, iliolumbar, lateral sacral	Inferior epigastric, deep circumflex iliac
Primary territory	Pelvic viscera, perineum, gluteal and pelvic muscles, sacrum	Lower anterior abdominal wall, then the entire lower limb
Becomes	Terminal branches within the pelvis	Femoral artery at the inguinal ligament
Clinical consequence of occlusion	Buttock claudication, erectile dysfunction, pelvic ischemia, rectal ischemia	Leg claudication, acute limb ischemia

The clinical asymmetry is stark. Blocking or covering the external iliac artery threatens the leg and produces symptoms most clinicians recognize immediately. Blocking or covering the internal iliac artery threatens the pelvis, and the resulting ischemia can be subtle at first. That is why so much endovascular research focuses on preserving internal iliac flow during aneurysm repair.

A case report of a 65-year-old man with a 43 mm left common iliac aneurysm and bilateral internal iliac aneurysms (right 41 mm, left 49 mm) described treatment with an aortobi-iliac stent graft and bilateral iliac branch devices, with extensions into opposing anterior and posterior divisions. He developed clinical signs of right-sided gluteal claudication at six weeks, but the symptoms resolved by 20 weeks [11]. That timeline is typical of pelvic ischemia after internal iliac coverage.

Why Internal Iliac Preservation Matters

When an endovascular stent graft lands in the common iliac artery, it can cover the origin of the internal iliac artery. That is sometimes unavoidable, but the consequences are real. Pelvic ischemic complications include buttock claudication and rectal ischemia [12]. A midterm study of the ELFIRE procedure (Endurant limb fenestration with internal iliac artery repair and enhanced preservation), which used a physician-modified fenestrated Endurant contralateral limb with a preloaded wire system and Viabahn VBX bridging stent grafts, analyzed 95 patients with a mean age of 78 years, 87.4% of them men, across 126 branches [12].

Several device strategies exist for keeping the internal iliac artery open. A 2026 report described three physician-modified Endurant configurations for internal iliac preservation in patients with common iliac bifurcation diameters of 18 mm or less: a single fenestration, an outer branch with a 6 × 10 mm PTFE graft, and a mini-inner branch with a 6 × 5 mm obliquely cut PTFE graft. Technical success was achieved in all 12 patients, with no type I or III endoleaks [13]. A separate case report described a custom-made single-fenestrated endograft used to preserve internal iliac flow in a 56-year-old man with a 56 mm abdominal aortic aneurysm involving the right common iliac artery, where a standard iliac branch device was not feasible because of narrow anatomy [14]. Custom-made fenestrated leg extensions have also been used for internal iliac artery aneurysms when iliac branch devices were unsuitable [15].

Common Iliac Artery Disease and Intervention

The common iliac artery is a common site of atherosclerotic occlusive disease and aneurysm formation. Chronic total occlusion of the common iliac artery is a technically challenging subset of aortoiliac occlusive disease, especially when the lesion extends close to the aortic bifurcation. A retrospective study of 30 consecutive patients with unilateral common iliac chronic total occlusion treated with a planned first-line bilateral femoral access strategy reported technical success in 93.3% of cases, with most lesions classified as TASC II C or D (86.7%). Periprocedural complications included access-site hematoma (6.7%), flow-limiting dissection (3.3%) and distal embolization (3.3%) [16].

Bifurcation lesions that involve the common, internal and external iliac arteries together are harder still. A 2026 case report described a 46-year-old man with lifestyle-limiting claudication from a heavily calcified iliac bifurcation lesion treated with a double-kissing double-crush technique, a strategy borrowed from coronary intervention. He remained asymptomatic with durable stent patency at 12 months [17].

Stent migration is a rare but recognized complication. A case report described a 64-year-old man with diabetes and hypertension who developed retrograde migration of a common iliac artery stent across the aortic bifurcation after iliac stenting, managed percutaneously. The authors emphasized adequate vessel preparation with intravascular imaging for prevention [18].

Common Mistakes and Limitations

Several recurring errors show up in how people think about iliac artery anatomy.

Assuming the bifurcation is always at L4. The L4 level is an average. Documented variants include a high bifurcation at L3 with an extremely short left common iliac artery [1], congenital absence of the left common iliac artery with division at L5 [2], and ordinary variation in the bifurcation-to-sacral-promontory distance [3]. Imaging before intervention resolves the question.

Treating the common iliac artery as branchless. About 19% of common iliac arteries have a detectable branch on angiography, and nearly half of those are aberrant vessels that replace a normal artery [5]. Some can supply the spinal cord.

Assuming the internal iliac artery always branches the same way. The branching pattern varies widely. The first branch of the anterior division is usually the umbilical artery, but the obturator artery has been documented as the first branch in at least one dissection [19]. The internal pudendal and inferior gluteal arteries can arise from a common trunk [19].

Confusing the internal and external iliac territories. The internal iliac artery is a pelvic and gluteal vessel. The external iliac artery is a leg vessel that happens to start in the pelvis. Symptoms after occlusion follow that split.

Forgetting that internal iliac branches can feed the spine. Spinal arteriovenous fistulas supplied by internal iliac branches are under-recognized and easily overlooked on spinal angiograms [8].

Overlooking external iliac endofibrosis in athletes. Exertional leg symptoms in endurance athletes are often attributed to musculoskeletal causes, and external iliac endofibrosis is typically underdiagnosed as a result [9][10]. Early diagnosis matters because acute ischemia can occur [9].

Individual anatomy varies, and any decision about imaging, diagnosis or treatment for a specific person requires evaluation by a qualified clinician.

Frequently Asked Questions

Where does the abdominal aorta bifurcate into the common iliac arteries?

The abdominal aorta typically bifurcates at roughly the L4 vertebral level. Documented variants range from a high bifurcation at L3 to division at L5, so imaging confirms the level in any given person [1][2].

How long is the common iliac artery?

A typical adult common iliac artery is about 4 to 5 cm long. Length varies, and unusually short segments limit the landing zone available for endovascular devices [4].

What is the difference between the internal and external iliac arteries?

The internal iliac artery supplies the pelvic organs, perineum and gluteal muscles. The external iliac artery runs along the pelvic brim, exits under the inguinal ligament and becomes the femoral artery of the leg.

What does the internal iliac artery supply?

It supplies the pelvic viscera, the perineum, the gluteal and lateral rotator muscles, the pelvic floor and parts of the sacrum and bony pelvis. Its branches divide into an anterior division and a posterior division [6][7].

What are the two branches of the external iliac artery?

The inferior epigastric artery and the deep circumflex iliac artery. Both arise just above the inguinal ligament.

Why is the internal iliac artery also called the hypogastric artery?

Hypogastric is the older term for the same vessel. Both names refer to the internal iliac artery and its anterior and posterior divisions.

What happens if the internal iliac artery is blocked?

Pelvic ischemic complications can include buttock claudication and rectal ischemia [12]. Symptoms may appear weeks after the procedure and can improve over time, as in a reported case where gluteal claudication present at six weeks had resolved by 20 weeks [11].

Can iliac artery anatomy vary between people?

Yes, substantially. Reported variants include a high aortic bifurcation with an extremely short common iliac artery [1], congenital absence of the left common iliac artery [2], anomalous common iliac branches [5], and unusual internal iliac branching patterns such as an obturator artery as the first branch [19].