Topics

Topic

design image
Descending mesocolon

The descending mesocolon is the fold of peritoneum that suspends the descending colon from the posterior abdominal wall. It develops embryologically as part of the dorsal mesentery of the hindgut, though in most adults it is secondarily fused to the posterior abdominal wall (retroperitoneal), while retaining its vascular and nervous structures. In rare cases, persistence of a mobile descending mesocolon may predispose to volvulus or internal herniation.

It carries the vascular supply, lymphatics, and autonomic nerves to the descending colon. Its arterial supply is derived from branches of the inferior mesenteric artery (IMA), while venous drainage parallels the arteries, draining to the inferior mesenteric vein (IMV) and then the portal venous system.

Clinically, the descending mesocolon is important in left hemicolectomy, colorectal cancer surgery, diverticular disease, ischemic colitis, and in rare cases of congenital non-fusion leading to volvulus.

Synonyms

  • Mesocolon of the descending colon

  • Left colonic mesentery

Function

  • Suspends the descending colon from the posterior abdominal wall (in fetal life; typically fused in adults)

  • Conveys arteries, veins, lymphatics, and autonomic nerves to the descending colon

  • Serves as an anatomical plane in colorectal resections and oncologic dissections

Nerve Supply

  • Sympathetic fibers from the lumbar splanchnic nerves via the inferior mesenteric plexus

  • Parasympathetic fibers from the pelvic splanchnic nerves (S2–S4)

  • Enteric nervous system plexuses regulate local motility and secretion

Arterial Supply

  • Left colic artery (branch of inferior mesenteric artery)

  • Small contributions from sigmoid arteries (IMA branches)

Venous Drainage

  • Left colic vein and tributaries drain into the inferior mesenteric vein (IMV)

  • IMV joins the splenic vein → portal vein

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 is hyperintense, vessels show signal voids

  • Colon wall edema or inflammation appears bright hyperintense

STIR:

  • Suppresses fat, highlighting inflammation, edema, or neoplastic infiltration of mesocolon

  • Useful in colitis and tumor spread evaluation

T1 Fat-Saturated (Pre-contrast):

  • Fat suppressed, vessels and bowel wall appear more clearly against hypointense background

T1 Fat-Saturated Post-Contrast (Gadolinium):

  • Mesocolic vessels enhance brightly

  • Colon wall shows uniform thin enhancement in normal state

  • Abnormal thickened heterogeneous enhancement suggests colitis or neoplasm

MRI Non-Contrast 3D Imaging:

  • Provides spatial visualization of descending mesocolon, vessels, and colon relationships

  • Useful in surgical planning and mapping vascular anatomy

CT Appearance

CT Pre-Contrast:

  • Mesocolon visualized as fat density with linear vascular structures

  • Colon wall thickening may be evident in pathology

CT Post-Contrast:

  • Arteries and veins enhance, defining the left colic vessels within mesocolon

  • Pathologies (diverticulitis, ischemia, tumor spread) show wall enhancement and mesocolic stranding

MRI images

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

MRI images

Descending mesocolon MRI sagittal image anatomy image -img-00000-00000

CT image

Descending mesocolon MRI sagittal image anatomy image -img-00000-00000