Inferior Mesenteric Artery Origin
The inferior mesenteric artery is a direct branch of the abdominal aorta. 1, 2, 3
Anatomical Origin and Location
The inferior mesenteric artery (IMA) arises as the third main unpaired anterior branch of the abdominal aorta, following the celiac trunk and superior mesenteric artery. 2, 4
Vertebral Level of Origin
- Most commonly originates at the L3 vertebral level (68-78.3% of cases) 3, 5
- Can arise at L2/L3 intervertebral disc level (3.3-22.5% of cases) 2, 5
- Less commonly originates at L4 (35% of cases) or L3/L4 (15% of cases) 2
- Rare origins include L2 (highest, 4.2%) and L5 (lowest, 2.5%) 2, 5
- The standard anatomical description places origin at the lower third of L3 4
Relationship to Other Aortic Branches
The IMA originates well below the other major anterior visceral branches:
- Celiac trunk: T12/L1 intervertebral disc level 4
- Superior mesenteric artery: Upper third of L1 4
- Renal arteries: Lower third of L1 4
- IMA: Lower third of L3 4
All three anterior visceral branches (celiac, superior mesenteric, and inferior mesenteric arteries) project to the left of the aortic midline in the horizontal plane. 4
Clinical Significance
Anatomical Stability
The IMA is considered very stable in its origin from the abdominal aorta, with direct aortic origin being the overwhelming norm. 6 This consistency makes it a reliable anatomical landmark during surgical and interventional procedures. 1
Rare Anatomical Variations
While the IMA almost always arises directly from the aorta, extremely rare variations have been documented:
- Anomalous origin from superior mesenteric artery: Only 9 cases reported in literature, representing an exceptionally rare embryological variant 6
- Such variations result from defective fusion of vitelline arteries during embryonic development 3
Surgical and Interventional Implications
Understanding the IMA's aortic origin is critical for:
- Mesenteric ischemia evaluation: CTA demonstrates the typical atherosclerotic origin lesions at the IMA ostium from the aorta 1
- Endovascular procedures: The aortic origin allows for selective catheterization and intervention when needed 1
- Colorectal surgery: Knowledge of the IMA's aortic origin and branching pattern is essential for left hemicolectomy, sigmoidectomy, and oncologic resections 6, 3
- Aortic aneurysm repair: The IMA origin must be identified and preserved or reimplanted during thoracoabdominal aortic procedures 1
The distance from the IMA root to the sacral promontory averages 99.58 ± 13.07 mm, which increases when the IMA origin is at a higher vertebral level. 5