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Accessory obturator vein

The accessory obturator vein (AOV) is an anatomical variant that accompanies the accessory obturator artery when present (10–30% of individuals). It usually arises from the external iliac vein or inferior epigastric vein, coursing along the superior pubic ramus toward the obturator canal, where it anastomoses with the obturator vein (draining into the internal iliac vein).

This vein may form part of the corona mortis (“crown of death”), an anastomotic venous (and sometimes arterial) connection between the external and internal iliac systems. This is clinically important in pelvic trauma, hernia repairs, and pelvic surgery, as injury can result in severe, sometimes fatal hemorrhage.

Synonyms

  • Aberrant obturator vein

  • Variant obturator vein

  • Venous component of corona mortis

Function

  • Provides collateral venous drainage between external and internal iliac venous systems

  • Drains blood from the obturator region, pubic bone, and adjacent pelvic structures

  • Acts as a potential pathway for collateral circulation in pelvic venous obstruction

  • Clinically relevant during hernia repair, orthopedic, gynecologic, and urologic surgery

MRI Appearance

T1-weighted images:

  • Vein appears as a linear hypointense structure along the superior pubic ramus

  • Surrounded by intermediate-to-high signal fat planes

T2-weighted images:

  • Normal vein lumen appears as a signal void due to fast blood flow

  • Thrombosis or slow flow may show hyperintense intraluminal signal

STIR:

  • Fat suppression enhances vein visibility against pelvic fat

  • Shows venous wall inflammation or perivascular edema as hyperintense regions

T1 Fat-Suppressed Post-Gadolinium:

  • Enhances brightly, outlining its course and anastomoses with obturator vein

  • Useful for detecting venous malformations, thrombosis, or extrinsic compression

MRV (Magnetic Resonance Venography):

  • Demonstrates the origin, course, and venous anastomoses of the AOV

  • Highlights corona mortis when present

  • Useful in preoperative venous mapping, trauma evaluation, and pelvic varicosity assessment

CT Appearance

Non-contrast CT:

  • Vein may be faintly visible as a tubular structure along superior pubic ramus

  • Often difficult to differentiate from adjacent fat and small vessels without contrast

CT Post-Contrast:

  • Enhances as a small but distinct vessel coursing toward the obturator canal

  • May reveal engorgement, compression, or collateral channels in pathology

CTV (CT Venography):

  • Clearly delineates the AOV and its connection to the obturator vein

  • Shows its role in corona mortis formation

  • Multiplanar and 3D reconstructions map venous variations and aid in surgical and trauma planning

  • Detects thrombosis, varicosities, or abnormal venous drainage pathways

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