The major vessels of the abdomen, including the abdominal aorta and the inferior vena cava, course along the posterior abdominal wall. Branches and tributaries of these vessels help supply and drain the posterior abdominal wall, and the abdominal viscera. Important lymphatic vessels that help with drainage of the lower body are also found in this area.

Let’s start off with the abdominal aorta, which gives rise to most of the arteries supplying the posterior abdominal wall. It transitions from the thoracic aorta to the abdominal aorta starting at the aortic hiatus, located within the diaphragm, at the level of the T12 vertebra. Then, it descends anterior to the vertebral bodies and ends at the level of the L4 vertebra.

From superior to inferior, the abdominal aorta has a number of structures associated with it anteriorly. These include the celiac plexus and ganglia, the body of the pancreas, the splenic vein, the left renal vein, the horizontal part of the duodenum and the coils of the small intestine.

Structures to the right of the abdominal aorta include the inferior vena cava, azygos vein, cisterna chyli, and the thoracic duct. Posteriorly, the left lumbar veins pass behind the aorta to reach the inferior vena cava.

Now, let’s talk about the various branches that arise from the abdominal aorta. These can be organized in three categories based on the “vascular plane” or direction in which the arteries branch from the abdominal aorta: first, there are paired visceral branches, that travel in the lateral plane; second, there are paired parietal branches, which travel in the posterolateral plane; and third, there are the unpaired visceral branches in the anterior midline plane.