The ascending lumbar vein is a vein that runs up through the lumbar region on the side of the vertebral column

Vertebral column

In human anatomy, the vertebral column is a column usually consisting of 24 articulating vertebrae, and 9 fused vertebrae in the sacrum and the coccyx. It is situated in the dorsal aspect of the torso, separated by intervertebral discs...

.

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 lateral sacral veins

Lateral sacral veins

The lateral sacral veins accompany the lateral sacral arteries on the anterior surface of the sacrum and end in the hypogastric vein....

, and it runs superiorly, intersecting with the lumbar veins

Lumbar veins

The lumbar veins are veins running along the inside of the posterior abdominal wall. They are the lumbar equivalent of the posterior intercostal veins.-See also:* Posterior intercostal veins* Subcostal vein* Ascending lumbar vein...

 as it crosses them.

When the ascending lumbar vein crosses the subcostal vein

Subcostal vein

The subcostal vein is a vein in the human body that runs along the bottom of the twelfth rib. It has the same essential qualities as the posterior intercostal veins, except that it cannot be considered intercostal because it is not between two ribs....

, it becomes one of the following:

• the azygos vein
  Azygos vein
  The azygos vein is a vein running up the right side of the thoracic vertebral column. It can also provide an alternate path for blood to the right atrium by allowing the blood to flow between the venae cavae when one vena cava is blocked.-Structure:...
  
   (in the case of the right ascending lumbar vein)
• the hemiazygos vein
  Hemiazygos vein
  The hemiazygos vein is a vein running superiorly in the lower thoracic region, just to the left side of the vertebral column.-Structure:...
  
  (in the case of the left ascending lumbar vein)

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