A discogram x-ray pictured
What is it?
A discogram is an enhanced X-ray examination designed to look specifically at theintervertebral discs in the spine. Dye is injected into the center of the injured disc(s) to make them clearly visible on X-ray film and on a fluoroscope, which is a special X-ray TV screen.
Why is it done?
The discogram is used to identify a disc or discs in the spine that have structural damage that may be causing pain. It can show whether a disc has begun to rupture and whether it has tears in the tough outer ring, called the annulus. This type of structural damage is a primary cause of pain within a damaged disc. Normal discs, and even those that are severely degenerated , do not usually cause pain.
A discogram is usually done after an MRI fails to show a herniated disc. Doctors also rely on the discogram when disc surgery is being seriously considered. The discogram is usually done prior to surgery to help the doctor determine the location of the problem and the type of operation that may be needed.
How is it done?
You will be given medication to help you relax. A local anesthetic is then applied to numb the area of the back to be tested. A long needle is inserted from the back into the nucleus pulposus , which is the very center of the intervertebral disc. A fluoroscope makes it possible for the doctor to see your spine and the needle as it moves. The doctor will watch the fluoroscope screen as the needle is inserted to make sure it goes into the correct disc space. Once the needle is inside the disc, a small amount of fluid is injected to cause an increase in pressure within the disc. More than one disc is tested to determine which levels are normal.
If the discogram causes pain that is similar to the back or leg pain you are experiencing, it is a good indication that the doctor has located the disc that is causing problems. Dye is then inserted into the disc, and X-rays are taken. Commonly, a CT scan is also done to see a cross section of the disc. The discogram procedure lasts about 40 minutes.
What are the limitations?
The discogram does not show the bones or nerves very well. It only shows the inside of the intervertebral disc.
What are the risks?
The discogram has more risks associated with it than most other tests used to diagnose spinal problems. For this reason, doctors prefer to use “noninvasive” tests first, such as the MRI and CT scan.
The risks associated with a discogram include infection inside the disc and an allergic reaction to the dye. Discograms require X-rays, which use radiation. In large doses, radiation can increase the risk of cancer. The vast majority of patients who have X-rays taken will never get enough radiation to worry about cancer. Only patients who must have large numbers of X-rays – hundreds over many years – need to be concerned.
A Patient’s Guide to Discograms of the Spine
What it is: A discogram is an X-ray examination of the intervertebral discs. The test is performed by injecting dye into the center of the injured disc(s). The dye makes the disc clearly visible on X-ray film and a fluoroscope screen.
What the test shows: This test is used to determine which disc(s) are damaged and if those discs are causing pain. This test will show if a disc has begun to rupture and will show if the disc has tears in the tough outer ring called the “annulus”. By injecting fluid to increase the pressure in the disc, the doctor can tell if the disc is painful. This is sometimes helpful in determining exactly which disc is causing the pain.
What the test does not show: The discogram is not a test that is done frequently. Usually the test is done after an MRI if the MRI fails to show a herniated disc. The discogram is normally done when surgery is being seriously considered, because the pain has not responded to treatment, and there is no evidence that the disc is actually herniated. The discogram does not really show the bones or the nerves that well – only the inside of the intervertebral disc.
How the test is done: A discogram is done by inserting a long needle into the center of the intervertebral disc itself – into the nucleus pulposus. The needle is inserted from the back. During a discogram, you will first be given medication to help you relax, and then a local anesthetic in the skin around the area of the back where the needle will be inserted. The doctor watches on a fluoroscope as he inserts the needle to make sure it goes into the correct disc space. The fluoroscope is a special X-ray TV that allows the doctor to see your spine and the needle as it moves. Once the doctor is sure the needle is in the disc space, he will inject a small amount of fluid to cause pressure in the disc space. If this causes pain, it is a good indication that the disc is abnormal. Dye is then inserted into the disc that will show up on X-rays. The X-rays are taken, and generally, a CAT scan is done as well, to see the disc in cross section. The procedure usually lasts about 40 minutes.
What risks the test has: A discogram requires a needle to be inserted into the disc. This test has more risks associated with it than most other tests. This is one of the reasons that doctors prefer to use the “non-invasive” tests, such as the MRI and CAT scan, first. The risks associated with a discogram include infection of the disc space, as well as an allergic reaction to the dye. Discograms are done using X-rays. X-rays use radiation, which in large doses can increase the risks of cancer. The vast majority of patients who get X-rays will never get enough radiation to worry about cancer. Only patients who must have multiple X-rays (hundreds) over many years need worry about this risk.
What the test costs: A discogram of the spine usually has two costs associated with the test. The first cost is the fee for actually doing the test. This is called the “technical fee”. The second cost is the fee of having a specialist, such as a radiologist or a spine surgeon, read and interpret the test. This is called the “professional fee”. You may get two bills for this test: one from the hospital or clinic where you had the discogram done, and one from the specialist who read the test.