The subcostal arteries are a pair of vessels that originate as the most inferior set from the descending thoracic aorta. They are in series with the intercostal arteries superiorly. The are termed subcostal because they tend to run inferior to the costal margin.
Having emerged from the aorta in the midline just superior to the aortic hiatus, the subcostal arteries run laterally over the body of T12. Then, each artery inclines inferiorly deep to the:
- splanchnic nerve
- paravertebral sympathetic trunks
- accessory hemiazygous vein on the left
- azygous vein and thoracic duct on the right
Each subcostal artery passes into the abdomen posterior to the lateral arcuate ligament in association with the subcostal nerve. It then passes around the upper abdomen parallel to the inferior border of the twelfth rib. During this course, it runs on the surface of quadratus lumborum, deep to the:
- respective kidney on each side
- ascending colon on the right
- descending colon on the left
Then, each subcostal artery pierces the aponeurosis of transversus abdominis anterior to the lumbar fascia. It passes anteriorly in the plane between transversus abdominis and the internal oblique muscle.
In the anterior abdominal wall, each subcostal artery anastomoses with branches of the:
- inferior intercostal arteries
- inferior epigastric arteries Posteriorly, it anastomoses with the lumbar arteries via dorsal branches akin to the dorsal branches of the posterior intercostal arteries.