From the Guidelines
For chronic leg pain with a negative physical exam, I would recommend starting with a non-contrast MRI. Non-contrast MRI is usually sufficient for evaluating most musculoskeletal causes of chronic leg pain, including muscle strains, tendinopathies, stress fractures, and many nerve compression syndromes 1. If the initial non-contrast MRI is inconclusive and there's clinical suspicion for conditions that would benefit from contrast enhancement (such as tumors, infection, or inflammatory processes), then a contrast-enhanced MRI could be ordered as a second step. Gadolinium contrast agents used in MRIs carry a small risk of allergic reactions and concerns about gadolinium deposition in tissues, so it's prudent to avoid unnecessary contrast when possible 1.
Some key points to consider when evaluating chronic leg pain include:
- The duration and character of pain
- Associated symptoms
- Risk factors
- Results of initial non-contrast MRI
These factors should guide your imaging approach and help determine if MRI is even necessary at this stage. Additionally, before ordering any imaging, ensure appropriate conservative measures have been tried, including physical therapy, anti-inflammatory medications like naproxen 500mg twice daily or ibuprofen 600mg three times daily for 1-2 weeks, and activity modification 1.
It's also important to note that the American College of Radiology (ACR) Appropriateness Criteria recommend non-contrast MRI as the initial imaging study for chronic leg pain, with contrast-enhanced MRI reserved for cases where there is a high suspicion of conditions that would benefit from contrast enhancement 1.
Overall, a non-contrast MRI is a reasonable first step in evaluating chronic leg pain with a negative physical exam, with contrast-enhanced MRI considered if the initial study is inconclusive or if there is a high suspicion of conditions that would benefit from contrast enhancement.
From the Research
MRI for Chronic Leg Pain
When considering an MRI for chronic leg pain with a negative exam, the decision to order an MRI with or without contrast depends on the specific clinical scenario.
- The use of contrast agents in MRI can provide additional information in certain cases, such as in the evaluation of musculoskeletal infections 2 or soft tissue tumors 3, 4.
- However, for chronic leg pain with a negative exam, the evidence is less clear. A study on acute shin splints found that MRI may be used to evaluate tibial pain in athletes, but the sensitivity and specificity were similar to those of triple-phase bone scan 5.
- The use of gadolinium-based contrast agents can increase reader confidence in diagnosis, but may not significantly improve the accuracy of diagnosis 3.
- In general, the choice of MRI with or without contrast should be based on the specific clinical question and the potential benefits and limitations of contrast agent use.
Considerations for Contrast Agent Use
When deciding whether to use contrast agents, consider the following:
- The potential benefits of contrast agent use, such as improved detection of certain conditions or increased reader confidence 2, 3.
- The potential limitations of contrast agent use, such as increased cost or potential adverse reactions 6.
- The specific clinical scenario and the potential impact of contrast agent use on diagnosis and treatment.