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Accessory obturator artery

The accessory obturator artery (AOA) is an anatomical variant present in approximately 10–30% of individuals. It typically arises from the external iliac artery or inferior epigastric artery, rather than the internal iliac system. When present, it runs along the superior pubic ramus toward the obturator canal, often forming an anastomosis with the obturator artery.

This artery is clinically significant because it may contribute to the vascularization of the obturator region, pubic bone, and medial thigh, and can create a corona mortis (Latin for "crown of death") when it forms a large pubic anastomosis between the external and internal iliac systems. Injury to this artery during pelvic or hernia surgery can result in life-threatening hemorrhage.

Function

  • Provides collateral circulation to the obturator territory when the main obturator artery is absent, small, or compromised

  • Supplies branches to the pubic bone, hip joint capsule, and adductor muscles

  • Clinically important in pelvic trauma, hernia repairs, orthopedic and gynecological surgery

MRI Appearance

T1-weighted images:

  • Artery appears as a small linear hypointense flow void coursing over the superior pubic ramus

  • Seen within bright perivascular fat of pelvis

T2-weighted images:

  • Artery lumen is a signal void

  • In thrombosed or diseased variants, lumen may appear hyperintense relative to surrounding fat

STIR:

  • Fat suppression makes the artery more visible within pelvic fat

  • Helps identify perivascular edema, hematoma, or inflammatory changes

T1 Post-Gadolinium (with fat suppression):

  • Artery enhances brightly and homogeneously

  • Useful for tracing the course, anastomoses, and presence of corona mortis

  • Highlights arterial wall thickening or tumor encasement if present

MRA Pelvis with Gadolinium:

  • Clearly delineates the origin, course, and anastomoses of the accessory obturator artery

  • Identifies connection with inferior epigastric artery, external iliac artery, or obturator artery

  • Excellent for detecting vascular variants prior to surgery

  • Useful in mapping pelvic vasculature in trauma, tumor embolization, or preoperative planning

CT Appearance

Non-contrast CT:

  • Artery not well seen without contrast

  • Can suggest its location along the superior pubic ramus by small vessel density

CT Post-Contrast:

  • Vessel opacifies clearly along superior pubic ramus

  • Detects vascular variants, aneurysms, or active bleeding

  • Important in trauma imaging when pelvic fractures are associated with hemorrhage

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