A discogram is a test used to evaluate back pain. A discogram is a test that generally isn't used for an initial evaluation of back pain. However, your doctor may suggest a discogram if your back pain persists despite conservative treatments, such as medication and physical therapy. During a discogram, dye is injected into the soft center of the disk. The injection itself sometimes reproduces your back pain. Several disks may be injected to try to pinpoint the cause of your back pain. The dye also moves into any cracks in the disk's exterior, which can then be seen on an x-ray or CT scan. Some doctors use a discogram before spinal fusion surgery to help identify which disks need to be removed. Typically, results of a discogram are combined with other tests such as an MRI or CT scan.