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Sigmoid veins

The sigmoid veins are tributaries of the inferior mesenteric vein (IMV) that provide venous drainage of the sigmoid colon. They accompany the sigmoid arteries and follow the course of the sigmoid mesocolon, draining blood from the mucosa, submucosa, and muscular layers of the sigmoid colon.

The sigmoid veins converge within the mesocolon to form several channels that unite with the IMV, which then drains into the splenic vein and subsequently the portal vein. These veins are clinically important as part of the portal venous system, and their anatomy is essential in understanding sigmoid colon diseases, ischemia, venous thrombosis, diverticular disease, inflammatory bowel disease, and colorectal surgery.

Because they communicate with systemic venous networks via collateral pathways, they may also play a role in portal hypertension and variceal formation.

Synonyms

  • Veins of the sigmoid colon

  • Venae sigmoideae

  • Inferior mesenteric tributaries

Function

  • Drain venous blood from the sigmoid colon into the inferior mesenteric vein

  • Contribute to the portal venous system returning blood to the liver

  • Act as potential collateral channels in portal hypertension

  • Important landmarks in colorectal surgery and interventional radiology

MRI Appearance

T1-weighted images:

  • Sigmoid veins appear as linear flow voids (black tubular structures) within the sigmoid mesocolon

  • Surrounded by intermediate signal colon wall and high-signal fat

T2-weighted images:

  • Appear as flow voids, with hyperintense bowel wall edema in inflammatory or ischemic conditions enhancing visualization

STIR:

  • Suppresses fat, improving detection of perivascular edema or inflammatory change

  • Makes small veins easier to trace within mesocolon

T1 Fat-Saturated (Pre-contrast):

  • Vein lumen appears intermediate signal, contrasting against suppressed mesocolon fat

T1 Fat-Saturated Post-Contrast (Gadolinium):

  • Veins enhance brightly and homogeneously during venous phase

  • Useful for identifying patency, thrombosis, or abnormal collaterals

MRV (Magnetic Resonance Venography):

  • Non-invasive mapping of sigmoid venous drainage

  • Depicts tributaries converging into IMV and its connection with splenic vein

  • Important for preoperative planning, ischemia assessment, and venous obstruction studies

CT Appearance

CT Pre-Contrast:

  • Veins appear as soft-tissue linear densities within mesocolon, often indistinct without contrast

CT Post-Contrast:

  • Veins enhance brightly in venous phase, draining toward the IMV

  • Useful for detecting thrombosis, extravasation, or congestion

CTV (CT Venography):

  • Best non-invasive method for defining sigmoid venous anatomy and variants

  • Provides 3D reconstructions of tributaries, their confluence into the IMV, and downstream portal drainage

  • Critical in portal hypertension, venous thrombosis, colorectal tumor mapping, and surgical planning

CT images

Sigmoid veins CT axial image 0

CT images

Sigmoid veins CT axial image 1

CT images

Sigmoid veins CT axial image 2

MRI images

Sigmoid veins MRI coronal anatomy image -img-00000-00000

MRI images

Sigmoid veins MRI coronal anatomy image -img-00000-00000_00001