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Inferior mesenteric artery (IMA)

The inferior mesenteric artery (IMA) is the third unpaired visceral branch of the abdominal aorta, arising at the level of L3, just below the origin of the renal arteries and typically 3–4 cm above the aortic bifurcation.

The IMA supplies the distal third of the transverse colon, descending colon, sigmoid colon, and upper rectum. Its major branches include:

  • Left colic artery – supplies descending colon

  • Sigmoid arteries – supply sigmoid colon

  • Superior rectal artery – terminal branch, supplying rectum

The IMA plays a vital role in the marginal artery of Drummond and arc of Riolan, which provide collateral pathways with the superior mesenteric artery (SMA). These anastomoses are essential in maintaining colonic perfusion during surgical resections or in cases of arterial occlusion.

Clinically, the IMA is important in ischemic colitis, aneurysms, mesenteric ischemia, surgical resections (low anterior resection, sigmoidectomy), and interventional procedures.

Synonyms

  • Arteria mesenterica inferior

  • Distal mesenteric artery

Function

  • Supplies arterial blood to the distal transverse colon, descending colon, sigmoid colon, and proximal rectum

  • Contributes to collateral circulation via marginal artery of Drummond and arc of Riolan

  • Provides critical perfusion to the left colon in cases of SMA occlusion

Branches

  • Left colic artery

  • Sigmoid arteries (2–4 branches)

  • Superior rectal artery (terminal branch)

MRI Appearance

T1-weighted images:

  • Appears as a flow void (black lumen) along the left retroperitoneum

  • Surrounded by hyperintense fat, aiding delineation

T2-weighted images:

  • Lumen appears as a dark signal void; bowel wall edema highlights arterial course in pathology

STIR:

  • Fat suppression improves artery visualization in mesenteric fat

  • Hyperintense perivascular changes indicate inflammation or ischemia

T1 Fat-Saturated (Pre-contrast):

  • Lumen demonstrates intermediate signal intensity, standing out against suppressed retroperitoneal fat

  • Helpful for locating vessel in non-contrast studies

T1 Fat-Saturated Post-Contrast (Gadolinium):

  • IMA enhances brightly and homogeneously, with branches clearly visible

  • Useful in mapping colonic vascularity and ischemia

MRA (Magnetic Resonance Angiography):

  • Clearly shows IMA origin from abdominal aorta, course, and branching pattern

  • Identifies stenosis, occlusion, aneurysm, or collateral networks

  • Useful in ischemic colitis workup and surgical planning

CT Appearance

CT Pre-Contrast:

  • Artery seen as a soft-tissue tubular structure anterior to the left psoas muscle

  • Limited visualization without contrast

CT Post-Contrast:

  • IMA opacifies brightly, showing origin and branches

  • Detects active bleeding, stenosis, or aneurysm

  • Surrounding fat stranding in ischemia or infection is readily visible

CT Angiography (CTA):

  • Gold standard for non-invasive evaluation

  • Provides detailed visualization of IMA origin, left colic, sigmoid, and superior rectal branches

  • 3D reconstructions demonstrate marginal artery and collateral pathways with SMA

  • Essential in planning colectomy, embolization, and diagnosing ischemia

MRI images

Inferior mesenteric artery (IMA) MRI coronal anatomy image -img-00000-00000

MRI images

Inferior mesenteric artery (IMA) MRI coronal anatomy image -img-00000-00000_00001

CT images

Inferior mesenteric artery (IMA) ct axial

CT images

Inferior mesenteric artery (IMA) ct coronal image

CT images

Inferior mesenteric artery (IMA) CT sag anatomy image -img-00000-00000

CT images

Inferior mesenteric artery (IMA)