Assessment and MRI for acute low back pain

Assessing a new episode

Acute refers to the duration of symptoms; it does not by itself mean that pain is either dangerous or mild. Low back pain may involve muscles and joints, but other causes also need consideration. A new episode should not automatically be assumed to be identical to a previous one.

Pain following a fall or accident, pain travelling into a leg, and associated fever, altered sensation or weakness may change the assessment. Simply identifying the location of pain is therefore not enough to decide what care or investigation is appropriate.

Symptoms requiring emergency assessment

New symptoms in the following list need emergency assessment when they accompany back pain. Their purpose is to help avoid delay, not to enable a diagnosis to be made at home.

Back pain after a serious accident, or back pain accompanied by chest pain, also needs emergency attention. Fever with feeling markedly unwell or severe pain that is worsening rapidly requires prompt medical care rather than waiting for a routine review.

• Difficulty starting to pass urine or inability to empty the bladder.
• New loss of bladder or bowel control.
• Reduced sensation around the genitals or anus.
• Significant or worsening weakness or numbness affecting both legs.

Information that helps at an appointment

Assessment considers when the pain started, where it travels, previous episodes and existing medical conditions. Recent injury, unexplained weight loss, a history of cancer or symptoms suggesting infection are important to mention. A list of current medicines also helps provide a complete clinical picture.

Concrete examples show how symptoms affect function. These might include a shorter walking distance, difficulty on stairs, disturbed sleep or problems moving at work. Examination may assess movement, sensation and muscle strength as appropriate. A single test attempted at home cannot substitute for this process.

The role of MRI and other imaging

Routine imaging is not recommended for uncomplicated low back pain in non-specialist care. Referral to a specialist does not necessarily mean that an MRI will be needed. Imaging is considered when its result is likely to change the diagnosis or management plan.

This does not mean that pain is being dismissed. The important question is which investigation, if any, can answer a question raised by the clinical assessment. MRI, X-rays and other imaging methods serve different purposes. Pain intensity alone does not determine that everyone needs the same scan.

Reviewing symptoms that continue

After the first assessment, changes in symptoms and everyday function help guide follow-up. A previous reassuring examination should not be used as a reason to ignore new weakness, altered sensation, fever or bladder and bowel changes. New findings may require a different assessment.

When progress is limited, the activity plan, work demands and need for additional support can be reviewed. Follow-up is not only a repetition of a pain score. It also identifies which parts of ordinary life remain difficult and whether the current approach needs adjustment.