Internal Iliac Artery Branches: Divisions & Functions

The internal iliac artery splits into two main trunks, a posterior division and an anterior division, and their branches collectively supply blood to nearly everything inside the pelvis: the bladder, rectum, reproductive organs, pelvic floor muscles, and the gluteal region of the buttock. This branching system is one of the most variable in the human body, with studies finding that the “textbook” pattern appears in only about 40% of people. That variability makes understanding these branches relevant well beyond the anatomy classroom, especially for surgeons, interventional radiologists, and anyone facing a pelvic procedure.

The Two Divisions at a Glance

The internal iliac artery (sometimes called the hypogastric artery) branches off the common iliac artery deep in the pelvis, usually at about the level of the sacroiliac joint. Within a few centimeters, it splits into a posterior division and an anterior division. The posterior division is the smaller of the two and generally sends its branches toward the pelvic wall and the gluteal muscles. The anterior division is larger and more complex, feeding the pelvic organs, the perineum, and additional muscles. In a small percentage of people, roughly 3% in one cadaveric study, the artery does not divide into two trunks at all and instead sends branches off individually from a single main stem.

Posterior Division Branches

The posterior division typically gives rise to three named arteries. Each one runs toward the back and side of the pelvis, supplying structures that support posture, walking, and spinal stability.

Iliolumbar Artery

The iliolumbar artery climbs upward behind the psoas muscle and splits into a lumbar branch and an iliac branch. The lumbar branch feeds the lower spinal muscles and sends small twigs into the spinal canal, while the iliac branch supplies the iliac fossa and part of the iliac bone itself. At its origin, this vessel averages about 3.5 mm in diameter, and it travels roughly 12 mm before splitting into its two terminal branches.

Some cadaveric work shows that the lumbar and iliac branches of this artery run close to the transverse process of the fifth lumbar vertebra and the nearby spinal nerve, which matters during spinal fusion surgery or approaches to the lumbosacral spine.

² The iliolumbar artery is also one of the most variable branches of the entire internal iliac system, with one South Indian cadaveric study documenting origin variations in 29% of cases.³

Lateral Sacral Arteries

Usually present as a superior and an inferior branch, the lateral sacral arteries descend along the front of the sacrum. They slip into the sacral foramina (the small holes on the front of the sacrum) and supply the sacral nerve roots, the meninges of the lower spinal cord, and the muscles and skin of the lower back. They are small vessels, but they become clinically relevant during sacral screw placement and sacral tumor surgery because puncturing them can cause troublesome bleeding in a confined space.

Superior Gluteal Artery

The superior gluteal artery is the largest branch of the entire internal iliac system. It exits the pelvis through the greater sciatic foramen, above the piriformis muscle, and immediately divides into a superficial branch (which fans out under the gluteus maximus) and a deep branch (which runs between the gluteus medius and minimus). The deep branch further splits into superior and inferior sub-branches that collectively supply four to seven perforating vessels to the gluteus medius and additional perforators to the gluteus minimus.

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The superior gluteal artery sits close to surgical corridors used for hip surgery and sacroiliac screw fixation. One study found that in about 45% of cases, the deep superior branch of this artery passed through the safe zone used for S1 sacroiliac screw entry points, a finding that highlights the bleeding risk during that procedure.⁵ For orthopedic surgeons, knowing where this artery lies is not academic trivia; it is a practical concern every time a screw is placed in the upper sacrum.

Anterior Division Branches

The anterior division carries more branches and feeds a wider range of organs and structures. The exact number and arrangement vary, but most anatomy references list six to eight named vessels.

Umbilical Artery and Superior Vesical Arteries

In fetal life, the umbilical arteries carry blood from the fetus to the placenta. After birth, most of each umbilical artery degenerates into a fibrous cord (the medial umbilical ligament, which you can sometimes feel through the abdominal wall). The portion that remains open, however, gives off the superior vesical arteries, which supply the upper part of the bladder. This open remnant is a convenient landmark in pelvic surgery because it reliably marks the path toward the bladder.

Obturator Artery and the Corona Mortis

The obturator artery typically runs along the lateral pelvic wall, passes through the obturator canal alongside the obturator nerve, and supplies the inner thigh muscles and the hip joint. The obturator artery is variable in its origin: in about a quarter of people studied in one cadaveric series, it showed significant origin variations.³

The variant that matters most clinically is the so-called corona mortis, Latin for “crown of death.” In this arrangement, an abnormal anastomosis crosses over the pubic bone, connecting the obturator artery (or vein) with vessels from the external iliac system. A study of Thai cadavers found an arterial corona mortis in about 23% of specimens, with a venous corona mortis occurring even more frequently.⁶ The name is dramatic but earned: this vessel crosses the exact area where surgeons place hardware to repair pelvic ring fractures, and cutting it accidentally can cause heavy, hard-to-control bleeding.

Uterine Artery

Present in females, the uterine artery crosses over the ureter (a relationship taught to medical students as “water under the bridge”) and reaches the uterus at the level of the cervix. It then sends ascending and descending branches along the sides of the uterus, supplying the body of the uterus, the cervix, and the upper part of the vagina. During pregnancy, this vessel undergoes dramatic remodeling: its lumen widens, it lengthens, and the vessel wall itself thickens through a combination of smooth muscle growth and tissue remodeling to accommodate the much higher blood flow the uterus demands.⁷

Inferior Vesical and Vaginal Arteries

The inferior vesical artery supplies the base of the bladder, the lower ureter, and, in males, the prostate and seminal vesicles. There has been debate about whether this artery exists in women or whether its territory is covered by the vaginal artery. A cadaveric study found that the inferior vesical artery was present in 92% of male specimens but also in about 47% of female specimens, sometimes arising from a trunk shared with the uterine artery.⁸ In the female cadavers where it was found, one of its terminal branches supplied the upper vagina, blurring the line between what is called the “inferior vesical” and what is called the “vaginal” artery. In practice, these are functionally overlapping vessels whose naming depends partly on convention.

Middle Rectal Artery

The middle rectal artery supplies the muscular wall of the rectum and connects with branches of the superior rectal artery (coming from above) and the inferior rectal artery (coming from below). This vessel is inconsistent. A cadaveric study of rectal arterial patterns found that the middle rectal artery could only be identified in about half of specimens, while the inferior rectal arteries were present in all of them.⁹ This means that surgeons performing low rectal resections cannot count on the middle rectal artery for consistent blood supply to the rectal stump; the inferior and superior rectal vessels do the heavier lifting.

Internal Pudendal Artery

The internal pudendal artery is the main blood supply to the external genitalia and the perineum. It exits the pelvis through the greater sciatic foramen alongside the inferior gluteal artery, hooks around the ischial spine, and re-enters the pelvis through the lesser sciatic foramen. From there it runs through the pudendal canal on the lateral wall of the ischiorectal fossa, giving off the inferior rectal artery, perineal branches, and finally the dorsal artery of the penis or clitoris. It often shares a common trunk with the middle rectal artery; one study found this shared origin in about 24% of cases.³

Inferior Gluteal Artery

The inferior gluteal artery exits the pelvis below the piriformis muscle, enters the gluteal region, and supplies the gluteus maximus, the hip rotator muscles, and the sciatic nerve’s own blood supply (the artery of the sciatic nerve). Rarely, the inferior gluteal artery persists as the dominant blood supply to the entire lower limb, a variant called a persistent sciatic artery. This embryonic vessel normally regresses, but when it does not, it runs alongside the sciatic nerve all the way down the back of the thigh. It is usually discovered incidentally on imaging and is rarely found on both sides.¹⁰

Why Variation Matters So Much

Few arteries in the body are as unpredictable as those of the internal iliac system. A large cadaveric study from South India found branching-pattern variations in 61% of hemipelvises examined, with the anterior division showing variations in 48% and the posterior division in 20%.³ A comprehensive review of internal iliac artery classifications noted that multiple classification systems have been proposed over the decades precisely because the branching pattern resists a single neat description.¹¹ A study in a Mexican population used Adachi’s five-type classification scheme on angiographic images to sort the patterns, confirming that the variation is not limited to any single ethnic group.¹²

For the interventional radiologist threading a catheter into a specific branch to stop bleeding, or for a surgeon identifying the uterine artery during a hysterectomy, the practical consequence is straightforward: you cannot assume the textbook picture matches what is actually there. Preoperative imaging with CT angiography has become the standard way to map a patient’s personal branching pattern before any elective pelvic vascular procedure.¹³

Uterine Artery Embolization

One of the highest-profile clinical applications of internal iliac artery anatomy is uterine artery embolization, a minimally invasive procedure in which a radiologist threads a catheter from the groin into the uterine artery and injects tiny particles to block blood flow. It is used to treat uterine fibroids (by starving them of blood supply) and to control life-threatening postpartum hemorrhage.¹⁴

For postpartum hemorrhage specifically, one series reported a clinical success rate of 85%, with uterine atony (the uterus failing to contract after delivery) being the most common reason for the procedure. In the cases where embolization failed, the patients required hysterectomy.¹⁵ The success of this procedure depends heavily on understanding the anatomy described above: the radiologist must identify the uterine artery’s origin, navigate any branching variants, and place the embolic material precisely enough to block the uterine supply without occluding neighboring branches that feed the ovary or bladder.

Internal Iliac Artery Ligation in Pelvic Trauma

Major pelvic fractures can shear through the internal iliac artery’s branches and cause catastrophic bleeding. When a patient is too unstable to be wheeled into an angiography suite for catheter-based treatment, surgeons may tie off one or both internal iliac arteries directly. This technique, called internal iliac artery ligation, works by dropping the pulse pressure inside the pelvic arterial network by as much as 85% after bilateral ligation. That dramatic slowdown in flow lets clots form at the bleeding sites and hold long enough for the body’s own clotting system to seal the damage.¹⁶

A study of hemodynamically unstable pelvic fracture patients found that bilateral ligation combined with pelvic packing achieved hemostasis in 18 patients, with the procedure taking about 65 minutes from start to completion of ligation. The authors described it as a potentially lifesaving option, especially in settings without access to angiography suites or interventional radiologists.¹⁷ A systematic review noted that the choice between ligation and angiographic embolization often comes down to the patient’s stability: unstable patients get taken straight to the operating room for ligation, while those who can be stabilized with fluids are sent for CT and angiography instead.¹⁸

The Pelvis’s Backup Blood Supply

One reason surgeons can safely tie off the internal iliac artery without causing widespread tissue death is the pelvis’s exceptionally rich collateral circulation. Blood finds alternative routes through connections between branches of the external iliac artery, the deep femoral artery, and the remaining patent internal iliac branches on the other side. A review of pelvic collateral pathways described the system as a “robust network” that can be classified into three main types based on how the rerouted blood travels: connections between internal organ vessels, connections between body-wall vessels, and connections between organ and body-wall vessels.¹³

After unilateral internal iliac artery interruption (as sometimes happens during aortic aneurysm repair), one of the major collateral pathways runs from the deep femoral artery through the medial femoral circumflex artery into the obturator artery, effectively reconnecting the thigh’s blood supply to the pelvic organs.¹⁹ This collateral system is why chronic occlusive disease of the iliac arteries can sometimes go unnoticed for years: blood slowly reroutes through these backup channels, and the patient’s pelvic organs stay adequately supplied, at least at rest.

What Goes Wrong When Collaterals Are Not Enough

Collateral circulation is good but not perfect. When the internal iliac artery is deliberately blocked during aneurysm repair, a meaningful percentage of patients develop ischemic complications. The two most common are buttock claudication (cramping pain in the buttock muscles during walking, caused by inadequate blood flow to the gluteal muscles) and erectile dysfunction.

A meta-analysis pooling results from multiple studies found that buttock claudication occurred in about 28% of patients after internal iliac artery exclusion, though nearly half of those cases resolved within about two years. Erectile dysfunction occurred in roughly 10% of males. Coil embolization of the internal iliac artery carried a higher rate of buttock claudication (about 33%) compared with simply covering the artery’s origin with a stent graft (about 13%). Bilateral treatment was associated with higher complication rates than unilateral treatment.²⁰

Smaller case series have reported even higher rates. One study of 29 patients found buttock claudication in 55% overall and new erectile dysfunction in 46% of men, with bilateral embolization carrying even worse numbers.²¹ A matched case-control study reported short-term buttock claudication in 71% of patients after internal iliac artery occlusion, though the rate dropped to 57% on longer follow-up.²² The variability across studies likely reflects differences in embolization technique, how far down the artery the blockage is placed, and how well the individual patient’s collateral network can compensate.

These complication rates are the reason vascular surgeons now make considerable effort to preserve at least one internal iliac artery whenever possible during aortic and iliac aneurysm repair. When both sides must be sacrificed, patients should be counseled beforehand that buttock pain with walking and, for men, sexual dysfunction are real and relatively common possibilities.

Mapping the Branches Before a Procedure

Given the frequency of anatomical variants and the stakes of getting the anatomy wrong, preoperative imaging has become central to pelvic vascular work. CT angiography is the most common tool. It allows radiologists to trace the internal iliac artery’s divisions, identify which branches come off which trunk, spot a corona mortis before it becomes a surgical surprise, and plan catheter routes for embolization. A review of angiographic anatomy in the male pelvis emphasized that once the larger branches are identified, smaller arteries and relevant variants become much easier to locate.²³

For procedures like uterine artery embolization or prostate artery embolization, the catheter work is guided by real-time fluoroscopy (live X-ray with contrast dye), but the radiologist goes in already knowing the patient’s unique branching pattern from the CT scan done days or weeks before. That preparation turns what would otherwise be a frustrating catheter hunt into a directed procedure, saving time and reducing the dose of contrast dye and radiation the patient receives. As pelvic endovascular procedures continue to expand, from fibroid embolization to hemorrhoid artery embolization, familiarity with the internal iliac system’s branches and their many variations has become one of the core competencies in interventional radiology.