The abdominal aorta

THE ABDOMINAL AORTA (Fig. 5.50; see also Fig. 6.11) The aorta enters the abdomen through the aortic hiatus of the diaphragm between the crura at T12 vertebral level. It lies anterior to L1-L4 vertebral bodies, close to the left psoas muscle. The left lumbar veins pass behind it. Anteriorly it is related to the pancreas, which separates it from the stomach, to the third part of the duodenum and to the coils of small intestine.

The abdominal aorta is 12 cm long and ends by dividing into the right and left common iliac arteries at L4 vertebral level.

Branches of the abdominal aorta

These are as follows: • Three unpaired anterior branches: — Coeliac trunk at T12/L1 — Superior mesenteric artery at L1 — Inferior mesenteric artery at L3 • Three lateral paired visceral arteries: — Adrenal arteries at L1 — Renal arteries at L1/L2 — Gonadal arteries at L3 • Five lateral paired parietal branches: — Inferior phrenic arteries at T12 — Four pairs of lumbar arteries; and • Terminal arteries: — The common iliac arteries — Median sacral artery.

Radiological features of the aorta

Plain films of the abdomen The aorta is visible only if calcified. It is then seen as linear calcification vertically in the midline and to the left of this. Tortuosity of the aorta in the elderly may cause considerable variation in the site of this calcification.

Proximity of the vertebral bodies may lead to bony erosion by aneurysms of the aorta, which may be detectable on radiographs.

Ultrasound

This is a useful means of studying the aorta, particularly for aneurysm formation. It can be visualized posterior to the pancreas, where its coeliac and superior mesenteric

Fig. 5.50 Major blood vessels. (b)