CAT scan - lumbar spine; Computed axial tomography scan - lumbar spine; Computed tomography scan - lumbar spine; CT - lower back DefinitionA 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 PerformedYou 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 TestSome 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.
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. Before having the contrast, tell your provider if you take the diabetes medicine metformin (Glucophage). You may need to take extra steps before the test if you take this drug. 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 as metal can affect the CT images. How the Test will FeelSome 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 PerformedCT scans rapidly makes detailed pictures of the lower back. The test may be used to look for:
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 ResultsResults are considered normal if no problems are seen in the lumbar region in the images. What Abnormal Results MeanAbnormal results may be due to:
RisksRisks of CT scans include:
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.
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. ConsiderationsThe 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. ReferencesGrawboski T, Gilbert TM, Larson EP, Cornett CA. Degenerative conditions of the cervical and thoracolumbar spine. In: Miller MD, Thompson SR, eds. DeLee, Drez, & Miller's Orthopaedic Sports Medicine. 5th ed. Philadelphia, PA: Elsevier; 2020:chap 130. Kapoor G, Toms AP. Current status of imaging of the musculoskeletal system. In: Adam A, Dixon AK, Gillard JH, Schaefer-Prokop CM, eds. Grainger & Allison's Diagnostic Radiology. 7th ed. Philadelphia, PA: Elsevier; 2021:chap 38. Williams KD. Fractures, dislocations, and fracture-dislocations of the spine. In: Azar FM, Beaty JH, eds. Campbell's Operative Orthopaedics. 14th ed. Philadelphia, PA: Elsevier; 2021:chap 41. | ||
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Review Date: 4/24/2023 Reviewed By: C. Benjamin Ma, MD, Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery, San Francisco, CA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. View References The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. No warranty of any kind, either expressed or implied, is made as to the accuracy, reliability, timeliness, or correctness of any translations made by a third-party service of the information provided herein into any other language. © 1997- A.D.A.M., a business unit of Ebix, Inc. Any duplication or distribution of the information contained herein is strictly prohibited. | ||
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