Lumbar veins

Anatomy and course

The four pairs of lumbar veins begin their course by arising from small venules that drain the skin and muscles of the posterolateral abdominal wall. They travel posteriorly along the posterolateral abdominal wall, alongside the corresponding lumbar arteries. Along the way, they receive tributaries from superficial veins of the anterolateral trunk; epigastric (superior, inferior), superficial epigastric, lateral thoracic and circumflex iliac veins.

As the lumbar veins continue along the wall of the posterior trunk, they usually pass posterior, or occasionally anterior to the lumbar part of the sympathetic trunk. Here, each lumbar vein drains blood from the sympathetic trunk and the lumbar portion of the deep back muscles.

Next, the lumbar veins continue towards the lumbar vertebrae. Anterior to the transverse processes of the lumbar vertebrae, the lumbar veins interconnect via two longitudinal vessels called ascending lumbar veins. There are two in total, one right and one left, corresponding to the right and left lumbar veins, respectively. Each ascending lumbar vein courses medially to the psoas major muscle and interconnects the ipsilateral lumbar, iliolumbar and common iliac veins. The ascending lumbar veins unite with the corresponding subcostal veins to form the azygos vein on the right and hemiazygos vein on the left. Occasionally, the ascending lumbar veins might drain into the first lumbar veins.

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The lumbar veins continue anteriorly along the anterolateral surfaces of the lumbar vertebral bodies. Here, they receive blood from the internal and external vertebral venous plexuses, draining the inferior two-thirds of the spinal cord. The lumbar veins also receive blood from the joints of the lumbar spine. From this point onwards, the trajectory of the lumbar veins can vary slightly. The third and fourth lumbar veins are constant and drain into the inferior vena cava. The left pairs are longer because they travel posterior to the abdominal aorta before reaching the inferior vena cava. In contrast, the first and second lumbar veins are quite variable. They can drain into several blood vessels, including the inferior vena cava, ascending lumbar veins, lumbar azygos veins or renal veins. The first and second lumbar veins can even empty into inferior lumbar veins.