Topography and Syntopy
The abdominal aorta begins at the aortic hiatus (hiatus aorticus) of the diaphragm at the level of the twelfth thoracic vertebra (Th12) and descends to the fourth-fifth lumbar vertebrae. The vessel lies retroperitoneally on the anterior surface of the lumbar spine, slightly to the left of the midline.
Relation to neighboring structures (syntopy):
- Superior and anterior: The aorta is related to the pancreas, the ascending part of the duodenum, and the root of the mesentery of the small intestine. The left renal vein (v. renalis sinistra) also crosses anterior to the aorta.
- Right: The inferior vena cava (v. cava inferior).
- Left: The left sympathetic trunk and intermesenteric plexus.
The aorta is surrounded by branches of the abdominal aortic plexus and ganglia. Left lumbar lymph nodes (pre-aortic, post-aortic, lateral aortic, and intermediate nodes) lie within the surrounding adipose tissue.
Branches of the Abdominal Aorta
The branches of the abdominal aorta are classified into visceral and parietal branches. At the L4 level, the aortic bifurcation (bifurcatio aortae) occurs, dividing into the right and left common iliac arteries (aa. iliacae communes).
Unpaired visceral branches:
- Celiac trunk (truncus coeliacus) — gives rise to the left gastric, splenic, and common hepatic arteries.
- Superior mesenteric artery (a. mesenterica superior).
- Inferior mesenteric artery (a. mesenterica inferior).
Paired visceral branches:
- Inferior phrenic arteries.
- Middle suprarenal arteries.
- Renal arteries (a. renalis dextra et sinistra).
- Gonadal arteries — testicular arteries (a. testicularis) in males or ovarian arteries (a. ovarica) in females. They have a high origin and a long course.
Parietal branches:
- Lumbar arteries (aa. lumbales I–IV) — paired segmental vessels running laterally posterior to the psoas major muscle. Anastomoses exist between the lumbar arteries and the deep circumflex iliac artery.
- Median sacral artery (a. sacralis mediana) — a slender unpaired vessel representing the continuation of the aorta, running downward along the anterior surface of the sacrum into the lesser pelvis.
Clinical Significance and Diagnostics
Comprehensive ultrasound and duplex scanning are used to evaluate the condition of the abdominal aorta, with CT angiography serving as the reference method. Aortic stiffness is assessed by measuring pulse wave velocity (PWV).
Topical clinical syndromes:
- Abdominal aortic aneurysm: Dilation of the vessel wall. Formation and dissection of an aneurysm cause sudden, severe abdominal pain.
- Visceral branch ischemia: Stenosis of the celiac trunk or mesenteric vessels leads to intestinal angina (angina abdominalis) — chronic ischemic abdominal pain triggered by increased peristalsis after meals. An abdominal bruit may be auscultated. Critical stenosis can lead to bowel infarction.
- Renal artery disease: Renal ischemia causes renovascular hypertension.
- Bifurcation lesions: Impair lower limb blood supply. Intermittent claudication (claudicatio intermittens) — walking pain, leg weakness, and decreased peripheral pulses — may occur.
Fun Fact: Phylogeny
In a closed single-circuit circulatory system, the heart may be absent. Its hemodynamic function is performed by the pulsating ventral aorta (aorta ventralis) and the bases of the afferent branchial arteries.