Anatomy Atlas

Inferior mesenteric artery

Arteria mesenterica inferior
Also: IMA
ArteryHigh-yielddraftCardioGI

Artery of the hindgut, arising from the aorta at L3. It supplies the distal transverse colon to the upper rectum, and its ligation during aortic surgery puts the watershed colon at risk.

Core anatomy

Location

Arises from the anterior aorta at about L3, behind the 3rd/4th part of the duodenum, 3–4 cm above the bifurcation.

Origin

Abdominal aorta

Course

Descends retroperitoneally to the left, crossing the left common iliac artery to become the superior rectal artery in the pelvis.

Branches
  • Left colic artery (descending colon, distal transverse colon)
  • Sigmoid arteries (sigmoid colon)
  • Superior rectal artery (upper rectum), its terminal branch
Supplies

Hindgut: distal third of the transverse colon, descending colon, sigmoid colon, upper rectum.

Anastomoses

The marginal artery (of Drummond) along the colon connects it with the middle colic (superior mesenteric artery). The superior rectal artery anastomoses with the middle and inferior rectal arteries (internal iliac). Watershed zones: splenic flexure and rectosigmoid.

Relations

The inferior mesenteric vein runs to its left and ascends to join the splenic vein. A horseshoe kidney is typically trapped beneath the IMA during its ascent.

Structures supplied

Mentioned in

Generated automatically from links in other entries.

Arterial supply of the gutCeliac trunk at T12 supplies the foregut, the superior mesenteric artery at L1 the midgut, and the inferior mesenteric artery at L3 the hindgut. The aorta bifurcates at L4.T12L1L2L3L4Abdominal aortaCeliac trunkSMAIMARenal aa.Common iliac aa. (L4)Foregutpain → epigastricStomachDuodenum (to papilla)LiverGallbladderPancreasSpleen**mesoderm; celiac supplyMidgutpain → periumbilicalDistal duodenum,jejunum and ileumAppendixcecum, ascending colon,proximal 2/3 of transverse colonHindgutpain → suprapubicDistal 1/3 transverse colon,descending and sigmoid colonUpper rectum (superior rectal a.)Watershed: splenic flexure, rectosigmoid

Swipe sideways to see the whole diagram →

Arterial supply of the gut. The three unpaired anterior branches of the abdominal aorta and their territories, with vertebral levels and where visceral pain from each region is felt.
Original schematic, created for this atlas.
Colon showing the inferior mesenteric artery with left colic, sigmoid and superior rectal branches
The inferior mesenteric artery and its branches.
Henry Vandyke Carter, Gray's Anatomy of the Human Body, 20th ed. (1918), Fig. 537. Source · Public domain (Public domain in the US: published before January 1, 1931 (per Wikimedia Commons))

Clinical correlations

Ischemic colitis after aortic surgery PANCE

Mechanism / lesion

The IMA is often sacrificed (or covered by an endograft) during AAA repair. If collaterals are poor, the left colon becomes ischemic.

Classic presentation

Left-sided abdominal pain and bloody diarrhea after aortic repair (the sigmoid and splenic flexure are most affected).

Horseshoe kidney

Mechanism / lesion

Fusion of the lower poles of the kidneys; ascent is halted when the isthmus catches under the IMA.

Classic presentation

Usually asymptomatic. Increased risk of obstruction, stones and infection. Associated with Turner syndrome.

High-yield PANCE pearls

  • IMA (L3) = hindgut: distal 1/3 transverse colon → upper rectum.
  • Branches: left colic, sigmoid, superior rectal.
  • Horseshoe kidney is trapped under the IMA.
  • Post-AAA repair bloody diarrhea → ischemic colitis (IMA territory).

Imaging anatomy

CT

CT angiography shows its origin, patency and the marginal artery; colonic wall thickening in ischemic colitis.

Key views & landmarks
  • CT angiography
  • Colonoscopy/sigmoidoscopy to assess ischemic colitis after aortic surgery

Physical exam

Strength / function testing

LLQ tenderness and bloody stool after aortic surgery should prompt evaluation for ischemic colitis.

Self-quiz

Q1.

At approximately which vertebral level does the IMA arise?

Show answer

D

The IMA arises at about L3; the celiac at T12 and the SMA at L1.

Q2.

A horseshoe kidney fails to ascend normally because the isthmus becomes trapped under which structure?

Show answer

C

The fused lower poles of a horseshoe kidney catch on the inferior mesenteric artery during ascent.

Q3.

Which is the terminal branch of the IMA?

Show answer

C

The IMA continues as the superior rectal artery into the pelvis. The middle rectal artery comes from the internal iliac; the middle colic from the SMA.

Q4.

Which artery is NOT a branch of the inferior mesenteric artery?

Show answer

B

The IMA gives the left colic, sigmoid and superior rectal arteries. The middle colic artery is a branch of the SMA; the marginal artery connects the two territories.

Q5.

The IMA supplies which part of the gut?

Show answer

D

The IMA (L3) supplies the hindgut: distal third of the transverse colon, descending and sigmoid colon, and upper rectum. The SMA supplies the midgut; the anal canal below the pectinate line is supplied by the inferior rectal arteries.

Flashcards

See also