The internal iliac artery, also known as the hypogastric artery, serves as a primary blood supply to various regions of the body. It originates from the common iliac artery at the level of the sacroiliac joint, marking a significant bifurcation point in the arterial system. This artery descends into the lesser pelvis, typically measuring about 3 to 4 cm in length. It provides blood to the pelvic walls, organs within the pelvis, the gluteal region, and the perineum.
The Posterior Division
The posterior division of the internal iliac artery primarily supplies the structures of the pelvic wall and gluteal region. This division typically gives rise to three main branches, each with a specific course and supply territory.
The iliolumbar artery is the first branch from the posterior division, traveling upward and laterally. It divides into a lumbar branch and an iliac branch. The lumbar branch supplies muscles like the psoas major and quadratus lumborum, while the iliac branch supplies the iliacus muscle and the iliac bone.
The lateral sacral arteries emerge, typically as two vessels—a superior and an inferior. These arteries extend medially, supplying structures within the sacral canal, including the sacral vertebrae and posterior sacrum muscles. They also contribute to the blood supply of the cauda equina.
The superior gluteal artery is the largest branch of the internal iliac artery’s posterior division and is often considered a continuation of the posterior trunk itself. This artery exits the pelvis by passing through the greater sciatic foramen, above the piriformis muscle. It then divides into superficial and deep branches, supplying the gluteal muscles.
The Anterior Division
The anterior division of the internal iliac artery is a network of vessels primarily responsible for supplying the pelvic organs, known as visceral supply, along with certain pelvic wall and thigh muscles. This division continues its trajectory towards the ischial spine. Its numerous branches ensure comprehensive blood distribution throughout the pelvic cavity and beyond.
Among the parietal branches, the obturator artery runs anteromedially along the lateral pelvic wall, exiting the pelvis through the obturator foramen. This artery supplies muscles in the medial thigh, such as the obturator externus and adductor muscles, and provides a branch to the head of the femur. The internal pudendal artery descends laterally towards the greater sciatic foramen, curving around the ischial spine to enter the perineum. It supplies the external genitalia and perineal muscles. The inferior gluteal artery also emerges from this division, supplying the gluteal muscles, particularly the gluteus maximus, and contributing to the sciatic nerve’s blood supply.
Regarding the visceral branches, the umbilical artery is a remnant of fetal circulation, with its obliterated portion forming the medial umbilical ligament. The patent part of the umbilical artery typically gives rise to the superior vesical artery, which supplies the superior aspect of the urinary bladder and the distal ureter in both sexes. In males, it also supplies the proximal part of the ductus deferens and seminal vesicles. The inferior vesical artery, commonly found in males, supplies the base of the bladder, the prostate gland, and the seminal vesicles. The middle rectal artery supplies the rectum, anastomosing with other rectal arteries.
Sex-Specific Branches and Anatomical Variations
The branching patterns of the anterior division of the internal iliac artery exhibit notable differences between sexes, reflecting the distinct reproductive anatomies.
In females, the uterine artery is a branch typically running inferomedially within the broad ligament to supply the uterus. The vaginal artery, also female-specific, usually arises near the uterine artery or sometimes from the umbilical artery, providing blood supply to the vagina, the inferior bladder, and the lower ureter.
In males, the inferior vesical artery serves as a counterpart, supplying the prostate gland and seminal vesicles, and sometimes giving off the artery to the ductus deferens. The artery to the ductus deferens, which supplies the ductus deferens, may also originate from the superior vesical artery. While the inferior vesical artery is more consistently present in males, its territory in females is often covered by branches of the vaginal or uterine arteries.
Beyond sex-specific branches, the internal iliac artery’s branching pattern varies across individuals. A common variation concerns the origin of the obturator artery. While it commonly arises from the anterior division of the internal iliac artery (in about 77.7% of cases), it can also originate from the external iliac artery, often via the inferior epigastric artery, in approximately 22.3% of individuals. Less common variations include its origin from the posterior division of the internal iliac artery or other branches.
Clinical Relevance in Medicine
Understanding the intricate anatomy of the internal iliac artery and its branches is important in various medical contexts. Its role in supplying the pelvic region makes it a focus in procedures involving hemorrhage control. In cases of severe pelvic bleeding, such as from trauma or postpartum hemorrhage, surgical ligation or embolization of the internal iliac artery can reduce blood flow to the affected area.
The artery also serves as an anatomical landmark during pelvic surgeries, including hysterectomies and resections for pelvic cancers. Surgeons rely on their knowledge of its course and branches to navigate the pelvic cavity, identify structures, and minimize the risk of iatrogenic injury. Awareness of its variations is important to avoid complications during these procedures.
Interventional radiology frequently targets branches of the internal iliac artery for therapeutic purposes. Procedures like uterine artery embolization, used to treat uterine fibroids, involve selectively blocking the uterine artery to reduce blood supply to the fibroids, leading to their shrinkage. Embolization is also employed to control bleeding from pelvic fractures or other vascular malformations within the pelvis.