The lumbar veins are four pairs of

veins Veins () are blood vessels in the circulatory system of 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 those of the pulmonary and fetal c ...

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 vi ...

, 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 the ...

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

thorax The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of 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 di ...

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.

Fate

The 3rd and 4th lumbar veins drain into the

. The fate of the two superior lumbar veins is 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.

Anastomoses

The 1st and 2nd lumbar veins are often interconnected with each other. An ascending lumbar vein additionally interconnects ipsilateral lumbar veins on each side. The lumbar veins communicate with the external and

internal vertebral venous plexuses The internal vertebral venous plexuses (intraspinal veins) lie within the vertebral canal in the epidural space, embedded within epidural fat. They receive tributaries from bones, red bone marrow, and spinal cord. They are arranged into four interc ...

, and form anastomoses with tributaries of the

azygos vein The azygos vein (from Ancient Greek ἄζυγος (ázugos), meaning 'unwedded' or 'unpaired') 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 superio ...

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, esse ...

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

. Bilateral asymmetry On the left side, the 3rd and 4th lumbar veins pass posterior to the

abdominal aorta In human anatomy, the abdominal aorta is the largest artery in the abdominal cavity. As part of the aorta, it is a direct continuation of the descending aorta (of the thorax). Structure The abdominal aorta begins at the level of the diaphragm ...

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 ascending lumbar vein, 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 ( ) 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 surgical procedure. ...

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

References

Thoracic veins Veins of the torso {{Circulatory-stub