Inferior Mesenteric Vein: Anatomy, Course, Tributaries, Relations, Function, Clinical Significance, MRI, CT & CTV Imaging

Topic

Inferior mesenteric vein

The inferior mesenteric vein (IMV) is a major venous channel that drains the large intestine and forms part of the portal venous system. It runs alongside the inferior mesenteric artery, receives tributaries from the left colon, sigmoid colon, and rectum, and typically terminates by joining the splenic vein. In some cases, it may join the superior mesenteric vein (SMV) or the junction of the SMV and splenic vein.

It is of clinical importance in portal hypertension, colorectal cancer staging, and surgical planning for colectomy and splenectomy.

Synonyms

IMV
Inferior mesenteric venous trunk
Left colic venous trunk (historical term in part)

Origin, Course, and Tributaries

Origin:
- Formed by the confluence of the superior rectal vein, sigmoid veins, and left colic vein
Course:
- Ascends in the retroperitoneum, typically to the left of the inferior mesenteric artery
- Passes posterior to the pancreas
- Usually terminates into the splenic vein, though variations exist
Tributaries:
- Left colic vein
- Sigmoid veins
- Superior rectal vein

Relations

Anteriorly: Peritoneum and descending colon
Posteriorly: Left psoas major muscle and retroperitoneal fat
Medially: Inferior mesenteric artery
Superiorly: Pancreatic body and splenic vein
Inferiorly: Rectum and pelvic colon

Function

Drains venous blood from the left colon, sigmoid colon, and rectum
Contributes to the portal venous circulation by emptying into the splenic vein
Plays a key role in conditions affecting colorectal venous return (portal hypertension, colorectal tumors)

Clinical Significance

Portal hypertension: May show dilation and development of collateral pathways
Colorectal carcinoma: IMV involved in venous drainage and tumor spread
Surgical relevance: Important landmark in colectomy and during high ligation of the inferior mesenteric vessels
Imaging: Assessed in portal venous imaging, oncologic staging, and venous thrombosis evaluation

MRI Appearance

T1-weighted images:

Vein lumen shows low signal intensity (flow void if patent)
Thrombosis may appear as intermediate-to-bright intraluminal signal

T2-weighted images:

Patent vein lumen shows low signal intensity due to flow void
Slow flow or thrombosis may produce bright intraluminal signal

STIR (Short Tau Inversion Recovery):

Flowing blood appears dark
Thrombosed segments may appear bright against suppressed fat

T1 Fat-Sat Post-Contrast:

Normal IMV enhances homogeneously with venous opacification
Thrombus: non-enhancing intraluminal filling defect
Perivenous inflammation or tumor invasion may enhance around the vessel

CT Appearance

Non-Contrast CT:

IMV appears as a soft tissue density tubular structure
Fresh thrombus may appear hyperdense compared to blood
Surrounded by retroperitoneal fat, providing contrast

Post-Contrast CT (Portal Venous Phase):

IMV enhances uniformly when patent
Thrombosis: intraluminal filling defect, expansion of the vein, and possible perivenous stranding
Tumor invasion: irregular narrowing, enhancing mass along vessel course

CT Venography (CTV) Appearance

Normal IMV: Well-opacified enhancing venous channel draining into the splenic vein
Thrombosis: Non-opacified segment with filling defect, expansion of lumen
Collateral pathways: Dilated alternative venous channels visible in portal hypertension
Tumor involvement: Extrinsic compression or enhancing intraluminal soft tissue mass may be seen
Pre-surgical mapping: CTV demonstrates IMV termination pattern (into splenic vein, SMV, or confluence), crucial for colectomy planning

MRI image

CT image

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