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.

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 (L1)
- inferior mesenteric artery (L3)
- median sacral artery
branches (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
- 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.

Paired branches to other viscera

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)