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External iliac artery

The external iliac artery (EIA) is the major terminal branch of the common iliac artery, arising at the level of the sacroiliac joint (around L5–S1). It runs along the pelvic brim, medial to the psoas major muscle, and passes beneath the inguinal ligament at the mid-inguinal point to continue as the femoral artery.

The EIA provides the primary arterial supply to the lower limbs, while also giving off important branches to the abdominal wall. Its close relationship with the inguinal ligament, lymph nodes, and pelvic structures makes it a critical vessel in vascular surgery, interventional radiology, and oncology.

Course

  1. Origin: Common iliac artery at sacroiliac joint.

  2. Pelvic course: Descends anteroinferiorly along medial psoas major, lateral to external iliac vein.

  3. Termination: Passes under inguinal ligament, becomes femoral artery.

Branches

  • Inferior epigastric artery: ascends into abdominal wall, anastomoses with superior epigastric artery.

  • Deep circumflex iliac artery: runs laterally toward ASIS, supplies abdominal wall.

  • Occasionally gives small pubic or iliac branches.

Synonyms

  • Arteria iliaca externa

  • External branch of common iliac artery

Function

  • Principal arterial supply to lower limbs via femoral artery continuation.

  • Contributes to abdominal wall vascularization via inferior epigastric and deep circumflex iliac arteries.

  • Plays a role in collateral circulation with internal iliac branches during pelvic or aortic occlusive disease.

MRI Appearance

T1-weighted images:

  • Appears as a linear hypointense flow void within bright perivascular fat.

  • Vessel wall hypointense, lumen voided due to flow.

T2-weighted images:

  • Lumen: signal void (normal fast flow).

  • Pathology: thrombus or dissection shows abnormal intermediate/hyperintense signal.

STIR:

  • Suppresses fat, delineating artery in pelvis.

  • Detects perivascular edema, hematoma, or inflammatory change.

T1 Fat-Suppressed Post-Gadolinium:

  • Artery enhances brightly and homogeneously.

  • Useful for identifying stenosis, aneurysms, vascular tumors, or inflammatory arteritis.

MRA Pelvis with Gadolinium:

  • Provides 3D visualization of EIA origin, course, and branches.

  • Identifies stenosis, occlusion, aneurysm, dissection, and vascular variants.

  • Excellent for pre-surgical vascular mapping, stent planning, and oncology assessment.

CT Appearance

Non-contrast CT:

  • EIA visible as a tubular soft-tissue density along medial border of psoas major.

  • Detects vascular calcifications, mural thrombus, or surrounding masses.

CT Post-Contrast:

  • Vessel enhances sharply, lumen clearly delineated.

  • Useful for detecting active extravasation, mural thrombus, or compression by pelvic masses.

CT Angiography (CTA):

  • Gold standard non-invasive technique.

  • Shows origin, bifurcation, course, and branches with high-resolution 3D reconstructions.

  • Detects stenosis, occlusions, aneurysms, dissections, vascular malformations, and pelvic trauma bleeding.

  • Critical for endovascular planning and bypass surgery evaluation.

CT VRT 3D image

external iliac artery CT 3D VRT anatomy image

CT image

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MRI image

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