A discogram is an invasive test that generally isn't used for an initial evaluation of back pain. But your doctor may suggest a discogram if your back pain persists despite conservative treatments, such as medication and physical therapy.
Some doctors use a discogram before spinal fusion surgery to help identify which disks need to be removed. However, discograms are not always accurate in pinpointing which disks, if any, are causing back pain. Many doctors instead rely on other tests, such as MRI and CT scanning, to diagnose disk problems and guide treatment.