A computed tomography (CT) scan, commonly referred to as a CAT scan, is a type of X-ray that produces cross-sectional images of a specific part of the body. In the case of a lumbar spine CT scan, your doctor can see a cross-section of your lower back. The scanning machine circles the body and sends images to a computer monitor, where they are reviewed by a technician.
The lumbar portion of the spine is a common area where back problems occur. The lumbar spine is the lowest portion of your spine, and is made up of five vertebral bones, including the sacrum and the coccyx (tailbone). Large blood vessels, nerves, tendons, ligaments, and cartilage are also part of the lumbar spine.
A CT scan is one of many imaging tests your doctor may use to investigate problems with your spine, such as pain due to injuries, disease, or infection.
Reasons your doctor might order a lumbar CT scan include:
- back pain accompanied by fever
- birth defects affecting the spine
- a herniated disk
- injury to the lower spine
- low back pain
- multiple sclerosis
- a pinched nerve
- problems controlling the bladder
- signs of cancer
- spinal surgery preparation
- weakness, numbness, or other problems with your legs
A CT scan is not the same as an MRI (magnetic resonance imaging) scan. An MRI of the lumbar spine shows the bones, disks, and spinal cord, as well as the spaces between the vertebral bones that nerves pass through. (RadiologyInfo.org)
A lumbar spine CT scan carries very few risks, but the contrast dye used during the procedure can cause temporary kidney damage. This risk is higher if your kidneys have already been damaged by disease or infection. However, newer dyes carry much less risk to the kidneys, and allergic reactions are extremely rare.
As with any X-ray, there is some exposure to radiation. While typically harmless, it is an important issue for women who are pregnant or could be pregnant. The amount of radiation used is considered safe for adults, but not for a developing fetus.
A lumbar spine CT scan is a noninvasive test.
You may want to wear loose, comfortable clothing because you will be required to lie down on a table. You’ll also be instructed to remove any jewelry and other metallic items from your body. Tell your doctor if you have any metal implants from prior procedures.
Before going into your CT scan, tell your doctor if you have any of the following conditions:
- allergy to oral contrast (barium)
- diabetes, as fasting may lower your blood sugar levels
CT scans are performed in a hospital’s radiology department or a clinic that specializes in diagnostic procedures.
A technician will ask you to lie on your back during the test. He or she may use pillows or straps to ensure that you stay in the correct position long enough to get a quality image. You may also have to hold your breath during brief individual scans.
The CT technician will move the table—via remote from a separate room—into the CT machine. You may go through the machine several times. (NIH)
Depending on the reason for your scan, you may be hooked up to an IV so that contrast dye can be injected into your veins during the test. This dye helps the machine take clear images of your blood vessels and organs.
After a round of scans, you may be asked to wait while the technician reviews the images to ensure they are clear enough that your doctor can read them correctly.
A typical CT scan takes between 30 and 45 minutes to complete.
After the test, you can change back into your street clothes and go about your day.
Results from a CT scan typically take a day to process. Your doctor will schedule a follow-up appointment to discuss the results of your scan and tell you how to proceed depending on the findings. He or she may order additional imaging scans, blood tests, or other diagnostic measures to help you get an accurate diagnosis and begin treatment.