Lumbar spine CT scan

A computed tomography (CT) scan of the lumbar spine makes cross-sectional pictures of the lower back (lumbar spine). It uses x-rays to create the images.

How the Test is Performed

You will be asked to lie on a narrow table that slides into the center of the CT scanner.

Once you are inside the scanner, the machine's x-ray beam rotates around you. (Modern "spiral" scanners can perform the exam without stopping.)

A computer creates separate images of the spine area, called slices. These images can be stored, viewed on a monitor, or printed on film. Three-dimensional models of the spine area can be created by adding the slices together.

You must be still during the exam. Movement can cause blurred images. You may be told to hold your breath for short periods of time.

The scan should take only 10 to 15 minutes.

How to Prepare for the Test

Some exams use a special dye, called contrast that is put into your body before the test starts. Contrast helps certain areas show up better on the x-rays.

Contrast can be given in different ways.

• It may be given through a vein (IV) in your hand or forearm.
• It may be given as an injection into the space around the spinal cord.

If contrast is used, you may also be asked not to eat or drink anything for 4 to 6 hours before the test.

Let your health care provider know if you have ever had a reaction to contrast. You may need to take medicines before the test in order to avoid this problem.

If you weigh more than 300 pounds (135 kilograms), find out if the CT machine has a weight limit. Too much weight can cause damage to the scanner's working parts.

You will be asked to remove jewelry and wear a hospital gown during the study.

How the Test will Feel

Some people may have discomfort from lying on the hard table.

Contrast given through an IV may cause a slight burning feeling, a metal taste in the mouth, and a warm flushing of the body. These feelings are normal and go away in a few seconds.

Why the Test is Performed

CT rapidly makes detailed pictures of the lower back. The test may be used to look for:

• Birth defects of the spine in children
• Injury in the lower spine
• Spine problems when MRI cannot be used

This test can also be used during or after an x-ray of the spinal cord and spinal nerve roots (myelography) or an x-ray of the disk (discography).

Normal Results

Results are considered normal if no problems are seen in the lumbar region in the images.

What Abnormal Results Mean

Abnormal results may be due to:

• Birth defects of the spine
• Bone problems
• Fracture
• Lumbar disk herniation

  Lumbar disk herniation

  A herniated (slipped) disk occurs when all or part of a disk is forced through a weakened part of the disk. This may place pressure on nearby nerves...

   

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• Lumbar spinal stenosis

  Spinal stenosis

  Spinal stenosis is narrowing of the spinal column that causes pressure on the spinal cord, or narrowing of the openings (called neural foramina) wher...

   

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• Spondylolisthesis

  Spondylolisthesis

  Spondylolisthesis is a condition in which a bone (vertebra) in the spine moves forward out of the proper position onto the bone below it.

   

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Risks

Risks of CT scans include:

• Being exposed to radiation
• Allergic reaction to contrast dye

CT scans expose you to more radiation than regular x-rays. Having many x-rays or CT scans over time may increase your risk for cancer. However, the risk from any one scan is small. Talk to your provider about this risk and how it weighs against the benefits of the test for your medical problem.

Some people have allergies to contrast dye. Let your provider know if you have ever had an allergic reaction to injected contrast dye.

• The most common type of contrast given into a vein contains iodine. If a person with an iodine allergy is given this type of contrast, nausea or vomiting , sneezing , itching , or hives may occur.

  Nausea or vomiting

  Nausea is feeling an urge to vomit. It is often called "being sick to your stomach. "Vomiting or throwing-up is forcing the contents of the stomach ...

   

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  Sneezing

  A sneeze is a sudden, forceful, uncontrolled burst of air through the nose and mouth.

   

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  Itching

  Itching is a tingling or irritation of the skin that makes you want to scratch the area. Itching may occur all over the body or only in one location...

   

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  Hives

  Hives are raised, often itchy, red bumps (welts) on the surface of the skin. They are usually an allergic reaction to food or medicine. They can al...

   

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• If you must have this type of contrast, you may get antihistamines (such as Benadryl) or steroids before the test.
• The kidneys help remove iodine out of the body. People with kidney disease or diabetes may need to receive extra fluids after the test to help flush the iodine out of the body.

Rarely, the dye may cause a life-threatening allergic response called anaphylaxis. If you have any trouble breathing during the test, you should tell the scanner operator right away. Scanners come with an intercom and speakers, so the operator can hear you at all times.

Considerations

The lumbar CT scan is good for evaluating large herniated disks, but it can miss smaller ones. This test can be combined with a myelogram to get a better image of the nerve roots and pick up smaller injuries.