Imaging/X-rays

Chances are, you don't need an X-ray or other tests to find out the cause of your pain. Most likely, it's a sprain or strain of the muscles. However, if your pain is more serious and doesn't go away, your doctor will do a medical history and a physical exam to find out the cause. The doctor may have you sit, stand and walk. Your reflexes will be tested with a rubber mallet.

Because the causes of chronic or severe lower back pain are so varied, doctors use several methods for detecting the source of your pain. If your doctor suspects an infection, a tumor, fracture or other problems, you will probably be referred for imaging scans.

X-rays: These may include the conventional X-ray scan, which means you get a low dose of radiation to see if you have any broken or injured bones. These are usually ordered before any other imaging studies.

Discography: Special dye is injected into the spinal disc that may be causing your pain. The dye helps outline the damaged areas on an X-ray. This is often used to assess chronic back pain.

Computed tomography: This is used for a ruptured disc or other damage caused to the vertebrae. X-rays are taken of the body at different angles. This gives a two-dimensional image (a "slice") of the back. This procedure is painless and does not involve surgery.

Magnetic resonance imaging (MRI): This is used to look at the lumbar region for bone breakdown or injury in tissues and nerves, muscles, ligaments, and blood vessels. Your doctor gets either a two-dimensional or three-dimensional image.

Electrodiagnostic procedures: These include three types of analyses: electromyography (EMG), nerve conduction studies and evoked potential (EP), EMG can look at the electrical activity in a nerve and can detect if muscle weakness results from injury or a problem with the nerves that control the muscle. Needles are inserted into the muscles to measure electrical activity. Nerve conduction studies involve two sets of electrodes placed on the skin. First you get a mild shock to stimulate the nerves. And then the nerve's electrical functioning is recorded. EP tests involve using two electrodes - one placed over the skin and the other placed on the scalp to record nerve signals.

Bone scans: Doctors use these to look for infection, fracture or other bone problems. Radioactive material is injected into the blood and collects in the bones. Images help the doctor see areas that have weakened bone.

Thermography: This uses infrared sensing devices to measure temperature changes between the two sides of the body. This can help see if nerves are compressed.

Ultrasound imaging: This uses high-frequency sound waves to get images inside the body. These can show tears in the ligaments, muscles, tendons and other tissues in the back.

This article was reviewed and updated June 2007.