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Ascending colon

The ascending colon is the first major segment of the colon (large intestine) located in the right side of the abdomen. It extends upward from the cecum at the ileocecal junction to the hepatic flexure beneath the right lobe of the liver, where it transitions into the transverse colon. It lies in the right lumbar and hypochondriac regions, anterior to the iliacus and quadratus lumborum muscles, and is retroperitoneal in most of its course.

The ascending colon’s primary functions are absorption of water, electrolytes, and vitamins (particularly vitamin K produced by gut flora), and the transport of fecal material toward the transverse colon. Its anatomy is clinically significant in right hemicolectomy, colon cancer staging, Crohn’s disease, ulcerative colitis, and diverticulitis.

Synonyms

  • Right colon

  • Right segment of large intestine

Function

  • Absorbs water, sodium, chloride, and vitamins from intestinal contents

  • Provides storage and propulsion of fecal matter

  • Supports gut microbiome fermentation processes

  • Contributes to immune and mucosal defense

Nerve Supply

  • Parasympathetic: Vagus nerve via the superior mesenteric plexus

  • Sympathetic: Lesser splanchnic nerves via the superior mesenteric ganglion

Arterial Supply

  • Ileocolic artery (branch of SMA)

  • Right colic artery (branch of SMA, variable)

  • Marginal artery of Drummond provides collateral supply

Venous Drainage

  • Ileocolic vein and right colic vein → superior mesenteric vein (SMV) → portal vein

  • Forms part of the portal venous system

MRI Appearance

T1-weighted images:

  • Colon wall shows intermediate signal intensity; lumen signal varies with contents (air = low signal, feces = mixed, fluid = intermediate)

  • Pericolic fat appears hyperintense, outlining the colon

T2-weighted images:

  • Bowel wall: intermediate to low signal

  • Fluid in lumen appears bright hyperintense

  • Wall thickening with hyperintensity may indicate inflammation or edema

STIR:

  • Suppresses fat, making wall edema, inflammation, and pericolic fluid collections more conspicuous

  • Useful in detecting inflammatory bowel disease and abscesses

T1 Fat-Saturated (Pre-contrast):

  • Colon wall appears intermediate signal, clearly differentiated from suppressed pericolic fat

  • Useful for assessing mural thickness

T1 Fat-Saturated Post-Contrast (Gadolinium):

  • Normal wall enhances thin and uniform

  • Abnormal patterns:

    • Layered or stratified enhancement → inflammatory bowel disease

    • Irregular heterogeneous enhancement → neoplasm

    • Absent enhancement → ischemia

MRI Non-Contrast 3D Imaging:

  • Allows multiplanar reconstructions for colonic length, wall thickness, and lumen caliber

  • Helpful in preoperative mapping and colon cancer staging

CT Appearance

CT Pre-Contrast:

  • Colon seen as a soft tissue wall with air or fecal contents in lumen

  • Detects calcifications, foreign bodies, and gross wall thickening

CT Post-Contrast:

  • Colon wall enhances uniformly when normal

  • Focal, asymmetric thickening with irregular enhancement → carcinoma

  • Diffuse, symmetric thickening with stratified enhancement → colitis or Crohn’s disease

  • Pericolic fat stranding indicates inflammation or infection

MRI image

Ascending colon MRI coronal anatomy image -img-00000-00000

CT images

Ascending colon ct axial image

CT images

Ascending colon ct coronal image

CT images

Ascending colon ct sag image