What is it?

Similar to a spinal nerve root block and facet joint block, a discogram is a test to determine the anatomical source of low back pain for the patient. This procedure is most frequently used to determine if degenerative disc disease is the cause of a patient’s pain (discogenic low back pain). Discograms are also performed to assist in preoperative planning for candidates for a lumbar spinal fusion.

In this procedure, the discographer inserts a needle in the patient’s back into the center of the disc. Radiographic dye is then injected into the disc, and if injecting the dye recreates the patient’s normal pain (concordant), it is then inferred that the specific disc is the source of pain for the patient. If the pain is unlike their normal pain (discordant) it can be inferred that even though the disc may look degenerated on an MRI scan, it is in fact not the source of the patient’s pain. The test itself is painful, but the patient needs to be awake and aware in order to tell the discographer what kind of pain is generated by the injection (see Figure 1 above).

As the discogram injection is not for treatment of pain, a steroid (anti-inflammatory medication) is not injected. However, sometimes a discographer will inject lidocaine (a numbing agent) into the disc to decrease the pain of the procedure. Often, after the discogram is completed, a CT scan is performed to check the morphology (anatomy) of the disc.

There are a limited number of risks involved with a discogram. Disc space infection is a serious but rare (<0.1%) potential complication. Because the needle passes close to the nerve, there is also slight risk of nerve root damage with the test.