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Pudendal vein

The pudendal vein (commonly referred to as the internal pudendal vein) is the principal venous channel draining the perineum and external genitalia. It accompanies the internal pudendal artery and pudendal nerve, running through the pudendal canal (Alcock’s canal) along the lateral wall of the ischioanal fossa.

It begins as a plexus of veins around the external genitalia and perineum — including tributaries from the penile (or clitoral) venous plexus, inferior rectal veins, and perineal veins. It then travels posteriorly, exits the perineum through the lesser sciatic foramen, loops around the ischial spine, and enters the pelvis through the greater sciatic foramen, ultimately draining into the internal iliac vein.

The pudendal vein is clinically important in conditions such as pelvic congestion syndrome, perineal varices, erectile dysfunction, trauma, and pelvic surgery complications.

Synonyms

  • Internal pudendal vein

  • Vena pudenda interna

  • Perineal venous plexus vein

Function

  • Drains venous blood from the perineum, external genitalia, and ischioanal region

  • Communicates with dorsal vein of penis/clitoris, vesical venous plexus, and inferior rectal venous plexus

  • Acts as a pathway for venous return into the internal iliac vein

  • Plays a role in erectile physiology and perineal venous circulation

MRI Appearance

T1-weighted images:

  • Pudendal vein appears as a linear hypointense structure in Alcock’s canal, adjacent to pudendal nerve and artery

  • Surrounded by high-signal fat for visibility

T2-weighted images:

  • Flowing blood: signal void

  • Venous varices or slow flow: hyperintense dilated channels

  • Detects venous engorgement in pelvic congestion

STIR:

  • Suppresses fat, highlighting venous dilatation and perivascular edema

  • Useful for identifying thrombophlebitis or varicosities

T1 Fat-Suppressed Post-Gadolinium:

  • Normal vein: bright homogeneous enhancement

  • Thrombosis: non-enhancing lumen with surrounding enhancement

  • Enhances visualization of venous plexus and pathological collaterals

MRV (Magnetic Resonance Venography):

  • Normal signal: flowing blood appears bright hyperintense on contrast-enhanced MRV

  • Thrombosed vein: appears as a hypointense filling defect

  • Provides a detailed map of pudendal venous plexus, connections to dorsal vein of penis/clitoris, and drainage to internal iliac vein

  • Excellent for evaluation of pelvic congestion syndrome, varices, or preoperative planning

CT Appearance

Non-contrast CT:

  • Pudendal vein usually not visualized

  • May be inferred as soft-tissue density within Alcock’s canal

CT Post-Contrast:

  • Enhances clearly as a venous channel accompanying pudendal artery and nerve

  • Detects venous dilatation, compression, or extrinsic invasion by tumor

CTV (CT Venography):

  • Normal signal: vein lumen opacifies as a bright hyperdense channel

  • Thrombosis: intraluminal filling defect surrounded by enhancing collaterals

  • Provides excellent visualization of pudendal venous plexus, varices, and communications with pelvic venous network

  • 3D CTV reconstructions are highly useful in surgical and interventional radiology planning

MRI image

Pudendal vein MRI axial anatomy image-img-00000-00000

CT image

Pudendal vein CT axial image 1

CT image

Pudendal vein CT axial image