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 tests show more detail than others. Doctors sometimes do imaging tests for low back pain to try to see the structures inside the back (figure 1).

The most commonly used imaging tests are:

●X-rays – These 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 – These are special kinds of X-ray. They show much more detail than X-rays. But they 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 – These create pictures 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 you 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.

If you have severe back pain, you might worry something is terribly wrong with your back. But most cases of back pain (even severe pain) are not caused by something serious. Low back pain usually goes away on its own or with simple treatment.

Doctors and nurses will usually wait 4 to 6 weeks before considering an imaging test for low back pain. This is true even if the pain is very bad. This is because the treatment for the first 4 to 6 weeks is usually the same no matter what is causing the pain. Plus, most people start to feel better after this time. But even without imaging, your doctor or nurse can still find out a lot about your back pain. They will do this by talking to 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:

●Is the pain just in your back, or does it spread to your buttocks or down your leg?

●Does 1 side hurt more than the other?

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

●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 happening with your back.

If you have certain symptoms, the doctor or nurse will know there might be something serious going on and order an imaging test.

Who should have imaging tests? — 

Imaging tests could be needed if you have had pain for 4 to 6 weeks or longer.

Your doctor or nurse might order an imaging test right away if you have certain symptoms. For example, you might need imaging if you:

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

●Are physically weaker due to aging or another health problem

●Have back pain with unexplained fever or weight loss

●Take "immune suppressants" or "steroid" medicines

●Have diabetes

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

●Use drugs you inject, such as heroin

●Have osteoporosis, a condition that weakens bones

●Have leg weakness or problems controlling your bowels or bladder

●Have "foot drop" – This is when you cannot hold your foot up (for example, while walking).

Why not have an imaging test just to check? — 

Although imaging tests are generally safe, they are not completely free of risk. The main reason to avoid doing an imaging test like an X-ray or CT scan is because these tests give off radiation. For example, an X-ray for low back pain can 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 give you even more radiation. For these reasons, doctors try to only do imaging tests when people really need them.

Also, people who have X-rays, CT scans, or MRIs are much more likely to have surgery and other invasive treatments than people who do not have imaging tests. That's because imaging tests can show "abnormal" findings. But abnormal findings are very common, even in people without back pain. This means people who probably would get better on their own might end up having surgery or other treatments.

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 get better over time without imaging tests. They can explain to you why imaging is not needed now, and work with you to come up with a treatment plan 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: Lumbar spinal stenosis (The Basics)

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