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Internal pudendal vein

The internal pudendal vein is a major venous channel of the pelvis and perineum, draining the external genitalia, anal region, urethra, and perineal musculature. It accompanies the internal pudendal artery and pudendal nerve through the pudendal (Alcock’s) canal and plays a critical role in venous return from erectile tissues and pelvic floor structures.

It originates from the deep dorsal vein of the penis or clitoris and receives branches from perineal and inferior rectal regions before emptying into the internal iliac vein. Because of its course in confined spaces and close association with pelvic neurovascular bundles, it is an important structure in pelvic surgery, urogenital procedures, and imaging assessment of perineal varicosities or vascular congestion.

Synonyms

  • Vena pudenda interna

  • Pudendal venous complex

Origin, Course, and Termination

Origin:

  • Begins as a continuation of the deep dorsal vein of the penis or clitoris, joined by perineal and erectile tissue venous tributaries.

Course:

  • Passes beneath the perineal membrane

  • Enters the pudendal (Alcock’s) canal, running with the internal pudendal artery

  • Courses along the lateral wall of the ischioanal fossa

  • Travels medially toward the pelvic cavity

Termination:

  • Drains into the internal iliac vein within the pelvic cavity

Relations

  • Anteriorly: Perineal membrane, urethra

  • Posteriorly: Ischioanal fossa fat, inferior rectal vessels

  • Superiorly: Pelvic diaphragm (levator ani)

  • Inferiorly: Perineal muscles (bulbospongiosus, ischiocavernosus)

  • Laterally: Obturator internus fascia forming Alcock’s canal

  • Medially: External anal sphincter and anal canal

Function

  • Drains venous blood from the penis, clitoris, perineum, inferior rectum, and pelvic floor

  • Plays a major role in venous outflow during erection and detumescence

  • Maintains venous circulation of perineal and urogenital structures

  • Important contributor to venous plexuses of the pelvis

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MRI Appearance

T1-weighted images:

  • Lumen shows low signal (dark) when blood flow is normal

  • Vessel walls are thin and low signal

  • Surrounding pelvic fat is bright, creating clear contrast

  • Slow flow may appear as intermediate intraluminal signal

T2-weighted images:

  • Flowing blood remains dark due to flow void and slow flowing blood appear bright

  • Venous walls appear thin and low signal

  • Surrounding soft tissues (muscle, pelvic floor structures): intermediate signal

  • Dilated veins show prominent dark tubular channels

STIR:

  • Fat is suppressed, aiding visualization of the low-signal venous lumen

  • Normal vein remains dark, set against suppressed fat planes

  • Enhances contrast between vessel and surrounding tissues

T1 Fat-Saturated Post-Contrast:

  • Venous lumen shows strong homogeneous enhancement

  • Enhances the entire course of the internal pudendal vein through Alcock’s canal

  • Pelvic soft-tissue contrast enables clear visualization of adjacent structures

  • No mural enhancement in normal anatomy

MRI image

Internal pudendal vein male image 1

MRI image

Internal pudendal vein male image 2

MRI image

Internal pudendal vein male image 3