Lower Back (Lumbar Spine) CT scan (without contrast)

What it is

The lumbar spine is the five large vertebrae of the lower back, sitting on the sacrum. A CT here produces thin slices through those bones and the spaces between them, which software can rebuild into side and three-dimensional views. The strength of the scan is bone detail: the exact line of a fracture, the amount of slippage of one vertebra on another, how much bone has grown into the channel where a nerve root exits. Disc material and the nerves themselves are visible but less distinctly than on an MRI, which is why the choice between the two tests depends on what the doctor is actually trying to see rather than on which is newer.

Why it is done

• To look for a fracture in the lower back after an injury, or a compression fracture in someone with thinning bone
• To assess narrowing of the spinal canal or the nerve exits, where the narrowing is caused by bone rather than soft tissue
• To check the position of screws, rods or a fusion after back surgery, in a setting where metal hardware would distort an MRI
• To image the lumbar spine in a patient for whom an MRI is not possible or not tolerated

What to expect

Patients lie on their back on a narrow table and are moved through the scanner ring. The scan itself lasts a few minutes. No IV is placed for this version and there is no dye, so there is no flush of warmth and no aftereffect — people drive themselves home. A separate procedure, a CT myelogram, involves injecting dye into the spinal canal with a needle before scanning; that is a different and much more involved appointment, with its own codes, and is not what this study is.

Questions worth asking

• Was an x-ray or an MRI of the same area also ordered? If several imaging tests of the lower back are being stacked in one episode of care, ask which one actually changes the plan.
• If a myelogram is recommended next, how many separate charges does it carry — the injection, the guidance imaging, the CT and the reading are usually billed as distinct items.
• Do I need prior authorization for lumbar imaging, and does my plan require a period of physical therapy first before it will pay?
• Is the scan being done in a hospital radiology department or at an outpatient center, and what is the difference in price here?