The lumbar veins are four pairs of

veins Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated b ...

running along the inside of the posterior

abdominal wall In anatomy, the abdominal wall represents the boundaries of the abdominal cavity. The abdominal wall is split into the anterolateral and posterior walls. There is a common set of layers covering and forming all the walls: the deepest being the ...

, and drain venous blood from parts of the abdominal wall. Each lumbar vein accompanies a single lumbar artery. The lower two pairs of lumbar veins all drain directly into the

inferior vena cava The inferior vena cava is a large vein that carries the deoxygenated blood from the lower and middle body into the right atrium of the heart. It is formed by the joining of the right and the left common iliac veins, usually at the level of th ...

, whereas the fate of the upper two pairs is more variable. Lumbar veins are the lumbar equivalent of the

posterior intercostal veins The posterior intercostal veins are veins that drain the intercostal spaces posteriorly. They run with their corresponding posterior intercostal artery on the underside of the rib, the vein superior to the artery. Each vein also gives off a dorsa ...

of the

thorax The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the cre ...

Structure

A lumbar vein accompanies each of the four

lumbar arteries The lumbar arteries are arteries located in the lower back or lumbar region. The lumbar arteries are in parallel with the intercostals. They are usually four in number on either side, and arise from the back of the aorta, opposite the bodies of ...

on each side of the body.

Distribution and tributaries

Collectively, the lumbar veins drain blood from the territories supplied by the corresponding lumbar arteries (the posterior, lateral, and anterior abdominal wall). The lumbar veins drain the

anterior spinal veins Anterior spinal veins (also known as anterior coronal veins and anterior median spinal veins) are veins that receive blood from the anterior spinal cord. Structure There are two major components to venous draining: the intrinsic vessels which drai ...

Fate

The 3rd and 4th lumbar veins drain into the

. The fate of the superior two lumbar veins us far more variable, and may drain into either the inferior vena cava, ascending lumbar vein, azygos vein, or (on the left side) the left renal vein; the 1st lumbar vein often passes inferiorly to join the 2nd lumbar vein, but may less commonly drain into the ascending lumbar vein, or the azygos vein; the 2nd lumbar vein may drain directly into the inferior vena cava (at or near the level of the renal veins), but may less commonly join the 3rd lumbar vein or drain into the

ascending lumbar vein The ascending lumbar vein is a vein that runs up through the lumbar region on the side of the vertebral column. Structure The ascending lumbar vein is a paired structure (i.e. one each for the right and left sides of the body). It starts at the c ...

Anastomoses

The 1st and 2nd lumbar veins are often interconnected with each other. An

additionally interconnects ipsilateral lumbar veins on each side. The lumbar veins communicate with external and internal vertebral venous plexuses, and form anastomoses with tributaries of the

azygos vein The azygos vein is a vein running up the right side of the thoracic vertebral column draining itself towards the superior vena cava. It connects the systems of superior vena cava and inferior vena cava and can provide an alternative path for blo ...

and

hemiazygos vein The hemiazygos vein (vena azygos minor inferior) is a vein running superiorly in the lower thoracic region, just to the left side of the vertebral column. Structure The hemiazygos vein and the accessory hemiazygos vein, when taken together, essen ...

(posteriorly), and (anteriorly) with branches of the epigastric veins, circumflex iliac veins, and lateral thoracic veins. The anastomoses formed by the lumbar veins provide a means of collateral veinous return.

Relations

The lumbar veins are

venae comitantes Vena comitans is Latin for accompanying vein. It refers to a vein that is usually paired, with both veins lying on the sides of an artery. They are found in close proximity to arteries so that the pulsations of the artery aid venous return. B ...

of the

. Each lumbar vein lies superior to its adjacent/corresponding lumbar artery (the same arrangement as in the intercostal neurovascular bundles). All of the lumbar veins lie posterior to the ipsilateral

sympathetic trunk The sympathetic trunks (sympathetic chain, gangliated cord) are a paired bundle of nerve fibers that run from the base of the skull to the coccyx. They are a major component of the sympathetic nervous system. Structure The sympathetic trunk lies j ...

. Bilateral assymetry On the left side, the 3rd and 4th lumbar veins pass posterior to the abdominal aorta to reach the inferior vena cava (which is displaced to the right of the midline); thus, the left 3rd and 4th lumbar veins are longer than the corresponding contralateral two lumbar veins.

Variation

There is variation in which lumbar veins drain to the

and which drain to the

, the

, and the

. A left lumbar vein may drain into the left renal vein.

Clinical significance

During central venous catheterisation of the

, the

catheter In medicine, a catheter (/ˈkæθətər/) is a thin tubing (material), tube made from medical grade materials serving a broad range of functions. Catheters are medical devices that can be inserted in the body to treat diseases or perform a surgi ...

may enter a lumbar vein. The catheter may need to be repositioned.

References

Veins of the torso {{Circulatory-stub