Abdominal aorta

The abdominal aorta (plural: aortas or aortae ⁴) is the main blood vessel in the abdominal cavity that transmits oxygenated blood from the thoracic cavity to the organs within the abdomen and to the lower limbs.

Summary

• origin: continuation of descending thoracic aorta at T12 

• course: descends anterior and slightly to the left of the lumbar vertebral bodies

• branches

  • unpaired

    • celiac artery (T12)

    • superior mesenteric artery (SMA) (L1)

    • inferior mesenteric artery (IMA) (L3)

    • median sacral artery

  • paired

    • middle adrenal arteries

    • renal arteries (L1-2)

    • gonadal arteries (between L2 and L3)

    • inferior phrenic arteries

    • lumbar arteries

• termination: bifurcates into right and left common iliac arteries at L4

• key relationships

  • posterior to the median arcuate ligament between two crura of diaphragm

  • anterior and slightly to the left of the lumbar vertebral bodies

  • inferior vena cava (IVC) is on its right

  • crossed anteriorly by the splenic vein and body of pancreas between the celiac and superior mesenteric artery origins

  • crossed anteriorly by the left renal vein, uncinate process of the pancreas and 3^rd part of the duodenum between the superior mesenteric and inferior mesenteric artery origins

Gross anatomy

Origin

It is a continuation of descending thoracic aorta at T12 posterior to the median arcuate ligament and diaphragmatic crura.

Course

It descends caudally in the retroperitoneum, anterior, and slightly to the left of the lumbar vertebral bodies. The IVC lies to its right.

Between the celiac and superior mesenteric artery origins, it is crossed anteriorly by the splenic vein and body of the pancreas and between the superior mesenteric and inferior mesenteric artery origins, it is crossed anteriorly by the left renal vein, uncinate process of the pancreas and 3^rd part of the duodenum.

The diameter of the aorta decreases from 28 mm in the thorax to less than 20 mm below the kidneys ⁵.

Termination

It eventually terminates at the L4 level by bifurcating into right and left common iliac arteries. This is also where the origin of median sacral artery is, which descends along the middle of sacral promontory.

Branches

Branches of the abdominal aorta can be thought of as belonging to a number of groups.

Single ventral branches (to the gut and related viscera)

• celiac artery (T12)

• superior mesenteric artery (L1)

• inferior mesenteric artery (L3)

Paired branches to other viscera

• middle adrenal arteries

• renal arteries (L2)

• gonadal arteries (between L2 and L3)

Paired branches to abdominal wall

• inferior phrenic arteries

• four paired lumbar arteries

Single parietal branches

• median sacral artery

Variant anatomy

• variable level of bifurcation

• right-sided aorta

• celiacomesenteric trunk

• sinuous course

• accessory renal artery

• direct branches, e.g. splenic, hepatic, accessory hepatic, accessory SMA, internal iliac

Related pathology

• abdominal aortic aneurysm

• abdominal aortic stenosis/occlusion: atherosclerosis, aortitis, Leriche syndrome