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Ascending mesocolon

The ascending mesocolon is the portion of the mesocolon that suspends the ascending colon from the posterior abdominal wall. It is a fold of peritoneum that encloses vessels, lymphatics, and nerves supplying the ascending colon. During embryological development, the ascending mesocolon usually fuses with the posterior parietal peritoneum, making the ascending colon secondarily retroperitoneal in most adults. However, in some individuals, a persistent mesocolon remains, which can be encountered surgically.

The ascending mesocolon transmits branches of the superior mesenteric artery (SMA) and superior mesenteric vein (SMV), lymphatics, and autonomic nerves to the ascending colon. Its anatomical relationships are clinically important in right hemicolectomy, mesocolic plane surgery, and oncological resections, where precise dissection ensures complete mesocolic excision with intact fascial planes.

Synonyms

  • Mesocolon of ascending colon

  • Right mesocolon

Function

  • Suspends the ascending colon and connects it to the posterior abdominal wall

  • Transmits arterial, venous, lymphatic, and neural supply to the ascending colon

  • Provides a surgical landmark in oncologic resection of right colon cancers

Nerve Supply

  • Autonomic innervation from the superior mesenteric plexus

  • Parasympathetic supply from the vagus nerve

  • Sympathetic fibers from the thoracic splanchnic nerves via SMA plexus

Arterial Supply

  • Branches of the ileocolic artery, right colic artery, and middle colic artery, all from the superior mesenteric artery (SMA)

Venous Drainage

  • Corresponding veins drain into the superior mesenteric vein (SMV), which contributes to the portal venous system

MRI Appearance

T1-weighted images:

  • Appears as a fatty peritoneal fold of high signal intensity containing intermediate-signal vascular structures

  • Colon wall is intermediate signal, making vessels within mesocolon distinguishable

T2-weighted images:

  • Mesocolon fat remains hyperintense, with vascular structures as signal voids

  • Inflammation or edema appears hyperintense within mesenteric fat

STIR:

  • Suppresses fat signal, allowing visualization of vascular bundles and inflamed or edematous mesocolon

  • Useful in detecting mesocolic inflammation, infection, or tumor infiltration

T1 Fat-Saturated (Pre-contrast):

  • Fat signal suppressed, enhancing visibility of vessels and soft-tissue abnormalities within the mesocolon

T1 Fat-Saturated Post-Contrast (Gadolinium):

  • Mesenteric vessels enhance brightly and homogeneously

  • Pathological conditions (e.g., tumor infiltration, mesocolic abscess, or peritoneal carcinomatosis) show heterogeneous enhancement

MRI Non-Contrast 3D Imaging:

  • Provides multiplanar visualization of vascular and mesenteric anatomy

  • Useful in pre-surgical planning and tumor mapping

CT Appearance

CT Pre-Contrast:

  • Mesocolon visible as fatty tissue planes with embedded vascular and lymphatic structures

  • Masses, hematomas, or calcifications can be identified

CT Post-Contrast:

  • Arteries and veins enhance brightly, clearly delineating SMA and SMV branches within the ascending mesocolon

  • Pathologies (tumors, inflammation, vascular anomalies) appear as enhancing or infiltrative changes within mesocolic fat

  • Crucial in oncology staging, trauma evaluation, and surgical planning

MRI images

ascending mesocolon MRI axial image anatomy image -img-00000-00000

MRI images

ascending mesocolon MRI coronal image anatomy image -img-00000-00000

MRI images

ascending mesocolon MRI coronal image anatomy image -img-00000-00000_00001

CT image

ascending mesocolon ct coronal image