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Sacral venous plexus

The sacral venous plexus is a network of interconnected veins located on the anterior surface of the sacrum, draining into the systemic and pelvic venous circulation. It lies within the extraperitoneal connective tissue and communicates with the internal vertebral venous plexus, providing an important venous pathway between the pelvis and spinal canal.

This plexus plays a major role in pelvic venous drainage and is clinically significant because it can act as a route for the spread of pelvic malignancies and infections to the spine.

Synonyms

  • Venous plexus of sacrum

  • Pelvic sacral plexus of veins

  • Presacral venous plexus

Origin, Course, and Drainage

  • Origin:

    • Formed by the convergence of small sacral veins arising from the anterior surface of the sacrum

  • Course:

    • Lies along the anterior surface of the sacrum, embedded in connective tissue

    • Communicates superiorly with the internal vertebral venous plexus via basivertebral veins

    • Connects laterally with the internal iliac veins through tributaries

  • Drainage:

    • Empties mainly into the internal iliac veins

    • Communicates with the lateral sacral veins and the median sacral vein

    • Provides collateral drainage between pelvic and vertebral venous systems

Relations

  • Anteriorly: Pelvic organs and parietal pelvic fascia

  • Posteriorly: Sacral bone and sacral foramina

  • Laterally: Internal iliac vessels and lumbosacral trunk

  • Superiorly: Communicates with lumbar venous plexuses

  • Inferiorly: Connects with the coccygeal venous plexus

Function

  • Provides venous drainage of the sacrum and presacral region

  • Acts as a venous communication pathway between pelvic veins and the vertebral venous plexus

  • Facilitates collateral circulation in cases of iliac vein obstruction

  • Provides potential routes for spread of infection or metastases from pelvis to spine

Clinical Significance

  • Important in the spread of pelvic cancers (e.g., rectal, prostate, cervical carcinoma) to vertebrae via Batson’s plexus

  • May contribute to presacral venous bleeding during pelvic or rectal surgery, which can be severe

  • Involved in pelvic venous congestion syndromes

  • Can be a site of thrombosis or engorgement in pelvic vascular disease

MRI Appearance

T1-weighted images:

  • Veins appear as flow voids (dark linear or tubular structures)

  • Thrombosed veins may appear as intermediate or bright signal intensity depending on stage of clot

T2-weighted images:

  • Flowing blood appears as signal voids

  • Engorged veins may show tubular signal voids against brighter pelvic fat

  • Thrombosis appears bright

STIR (Short Tau Inversion Recovery):

  • Suppresses fat, improving visualization of venous channels as dark flow voids

  • Thrombosis or inflammation may appear bright

T1 Fat-Sat Post-Contrast:

  • Veins enhance strongly with intravenous contrast

  • Thrombosed segments may show lack of enhancement

  • Surrounding inflammatory changes show enhancement

3D T2 SPACE / CISS:

  • Venous plexus appears as dark curvilinear flow voids surrounded by bright fat or CSF signal

  • Excellent for delineating venous channels adjacent to nerves and pelvic structures

CT Appearance

Non-Contrast CT:

  • Plexus appears as small soft tissue density channels along anterior sacrum

  • Thrombosis may appear as hyperdense foci within venous channels

Post-Contrast CT:

  • Veins enhance strongly, outlining the venous plexus against surrounding fat

  • Engorged plexus appears as multiple enhancing tubular structures

  • Thrombosed veins demonstrate filling defects with surrounding collateral vessel formation

MRI image

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MRI image

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CT image

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