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Transverse colon

The transverse colon is the longest and most mobile part of the large intestine, extending from the hepatic flexure (right colic flexure) to the splenic flexure (left colic flexure). It passes horizontally across the abdomen, suspended by the transverse mesocolon, which attaches it to the posterior abdominal wall. The transverse colon lies anterior to the small intestine and stomach, and its position may vary depending on posture and stomach distension. Structurally, it contains haustra, taeniae coli, and epiploic appendages, characteristic of the colon. Functionally, it serves as a site for water absorption, bacterial fermentation, and temporary storage of fecal material.

Synonyms

  • Colon transversum

  • Middle colon segment

  • Horizontal colon

Function

  • Absorbs water, electrolytes, and vitamins from intestinal contents

  • Houses gut microbiota for fermentation and nutrient processing

  • Mixes and stores fecal matter before passage to the descending colon

  • Contributes to overall fluid and electrolyte homeostasis

Arterial Supply

  • Primarily via the middle colic artery, a branch of the superior mesenteric artery (SMA)

  • Additional supply from:

    • Right colic artery (SMA branch) near hepatic flexure

    • Left colic artery (branch of inferior mesenteric artery, IMA) near splenic flexure

  • Arteries form the marginal artery of Drummond, providing collateral circulation

Venous Drainage

  • Drains into the superior mesenteric vein (SMV) via middle colic vein

  • At the splenic flexure, venous drainage connects with the inferior mesenteric vein (IMV)

  • Ultimately drains into the portal vein, linking the colon to the portal circulation

Nerve Supply

  • Parasympathetic innervation:

    • Proximal two-thirds: via vagus nerve (CN X)

    • Distal third (near splenic flexure): via pelvic splanchnic nerves (S2–S4)

  • Sympathetic innervation:

    • Proximal two-thirds: via superior mesenteric plexus

    • Distal third: via inferior mesenteric plexus

MRI Appearance

T1-weighted images:

  • Lumen with air appears as signal void (black)

  • Wall is low to intermediate signal intensity

  • Fat of the mesocolon is hyperintense, aiding contrast with colonic wall

T2-weighted images:

  • Lumen with fluid shows bright hyperintensity, air remains a signal void

  • Wall appears intermediate to low signal

  • Edema, inflammation, or tumors may appear as wall thickening with hyperintensity

STIR (Short Tau Inversion Recovery):

  • Fat suppression enhances detection of wall edema and pericolonic inflammatory changes

  • Inflamed colon (colitis, ischemia) appears hyperintense, while normal wall is low signal

T1 Post-Contrast (Gadolinium-enhanced):

  • Normal colon wall shows thin, homogeneous enhancement

  • Pathologies (cancer, colitis, ischemia) show thickened, heterogeneous, or asymmetric enhancement

  • Pericolonic vessels and mesenteric fat enhance distinctly

CT Appearance

Non-contrast CT:

  • Seen as a tubular structure with haustra, containing variable air, fluid, and fecal matter

  • Wall is of soft tissue density

  • Wall thickening, calcifications, or masses may be identified

Contrast-enhanced CT (CECT):

  • Wall demonstrates enhancement, useful for detecting colitis, tumors, ischemia, and diverticulitis

  • Hepatic and splenic flexures are key transition zones often involved in ischemia (“watershed areas”)

  • Multiplanar reconstructions show relation to mesentery and adjacent abdominal organs

MRI image

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

CT image

Transverse colon anatomy CT axial image -img-00000-00000

MRI image

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