Patient education: Do I need an X-ray (or other test) for low back pain? (The Basics)

What do imaging tests do? — Imaging tests, such as X-rays, create pictures of the inside of the body. Some do this in more detail than others. In the case of low back pain, doctors sometimes do imaging tests to try to see the structures inside the back (figure 1).

The most commonly used imaging tests are:

●X-rays – X-rays are good at showing bones, but they are not good at showing problems with "soft tissues." (Soft tissues include muscles and the rubbery discs found between each of the bones in the spine.) An X-ray can show if you have bones that are broken or out of place, or certain types of tumors or bone infections. X-rays might be also done if back pain is caused by an injury, such as a fall.

●CT scans – CT scans are a special kind of X-ray. They show much more detail than X-rays, but also expose you to more radiation and often cost more. CT scans can show all the problems that X-rays show, plus many problems with soft tissues.

●MRIs – MRIs are pictures that are created using powerful magnets, not radiation. They show more detail about soft tissues than CT scans. Some people can't have MRIs because they have metallic devices implanted in their body that would be affected by the magnet. Plus, MRIs are often expensive and people might have to wait to get them.

Do I need imaging if I have low back pain? — Most people with back pain do not need imaging.

When people have severe back pain, they often jump to conclusions and assume something is terribly wrong with their back. The truth is, most cases of back pain – even severe pain – are not caused by anything serious. Low back pain usually goes away on its own or with simple treatment.

If you see the doctor or nurse because of low back pain, do not ask for or expect to get an imaging test right away, unless you have one of the symptoms described below. Most people do not need an imaging test in the first 4 to 6 weeks of low back pain. In most cases, it does not make sense to order the test sooner, because the treatment for most causes of low back pain during those first few weeks is the same no matter what an imaging test might show. Even without an imaging test, your doctor or nurse can learn a lot about your pain – including what might be causing it and how to treat it – by talking with you and doing an exam.

How can the doctor or nurse tell what is wrong without an imaging test? — If you have low back pain, your doctor or nurse will do an exam and ask questions, such as:

●Do you have pain in just your back, or does it spread to your buttocks or down your leg?

●Is the pain the same on both sides, or does it affect one side more than the other?

●Do you have numbness, tingling, or weakness anywhere?

●Does the pain get better when you lean forward?

●Do you have any problems urinating or having bowel movements?

The results of the exam and your answers to these and other questions will give your doctor or nurse a good idea of what is going on with your back. If you have certain symptoms (discussed below), the doctor or nurse will know that there might be something serious going on and order an imaging test.

Who should have imaging tests? — People who have had pain for 4 to 6 weeks or longer often should have imaging tests to search for the cause. For people with certain symptoms, the doctor or nurse might want to order imaging tests right away. This includes people who:

●Had an accident or injury recently (such as a car crash or a fall)

●Are older

●Have back pain with unexplained fever or weight loss

●Take medicines called "immune suppressants" or medicines called "steroids"

●Have diabetes

●Have a history of cancer (except for skin cancer that isn't melanoma)

●Use drugs that you inject, such as heroin

●Have osteoporosis, a condition that weakens bones

●Have leg weakness or problems controlling their bowels or bladder

●Have a problem called "foot drop," which is when you cannot seem to hold your foot up, for example, while walking

Why not have an imaging test just to check? — People tend to think of imaging tests as harmless, but they are not harmless. The X-rays doctors use to try to diagnose back pain give as much radiation to your pelvic organs (ovaries or testicles) as you would get from having a chest X-ray every day for more than a year. CT scans expose you to even more radiation.

MRIs do not expose you to radiation but they still have risks. People who have MRIs (or other imaging tests) are much more likely to have surgery and other invasive treatments than people who do not have imaging tests. That's true even for people who do not need surgery. That's because "abnormal" findings on imaging tests of the back are very common, even in people without back pain. Abnormal findings can be scary, but they don't always mean that treatment is needed.

If your doctor or nurse does not think you need an imaging test for low back pain, it is OK to ask why. Doctors and nurses see many people with back pain who improve with time and do not need an imaging test. They can explain to you why imaging is not needed now, and work with you to come up with a treatment plan that you understand and are comfortable with.

More on this topic

Patient education: Low back pain in adults (The Basics)
Patient education: Herniated disc (The Basics)
Patient education: Vertebral compression fracture (The Basics)
Patient education: Spinal stenosis (The Basics)

Patient education: Low back pain in adults (Beyond the Basics)