MRI Without Contrast is the Imaging Modality of Choice
For a patient with persistent lower back pain who has failed 6 weeks of conservative therapy and is being considered for surgery or intervention, order an MRI of the lumbar spine without IV contrast. 1
Clinical Algorithm for Imaging Decision
First: Confirm the Patient Meets Imaging Criteria
You should only proceed with imaging if the patient meets both of the following:
- Failed 6 weeks of optimal conservative management (pharmacologic therapy, physical therapy, remaining active) 1
- Is a candidate for surgery or intervention, meaning you would actually change management based on imaging findings 1
Critical caveat: If the patient has not completed 6 weeks of conservative therapy and has no red flags, imaging provides no clinical benefit and increases healthcare utilization without improving outcomes. 1
Second: Screen for Red Flags That Change the Urgency
If any of the following neurologic deficits are present, imaging becomes urgent rather than routine:
- Motor weakness in the lower extremities 2
- Saddle anesthesia 2
- Bowel or bladder dysfunction 2
- Progressive or severe neurologic deficits 2, 3
- Bilateral leg weakness 2
These red flags indicate potential cauda equina syndrome or severe nerve compression requiring immediate evaluation to prevent permanent disability. 2
Third: Choose MRI Over CT
MRI lumbar spine without IV contrast is superior to CT for the following reasons:
- Excellent soft-tissue contrast that accurately depicts disc degeneration, the thecal sac, and neural structures 1
- No ionizing radiation exposure, particularly important in younger patients 2
- Better detection of serious conditions including spinal cord compression, malignancy, and infection 2
- Superior visualization of vertebral marrow, spinal canal, nerve roots, and intervertebral discs compared to CT 2
When CT May Be Appropriate Instead
CT should be reserved for specific circumstances:
- MRI contraindications: Patients with non-MRI-safe implanted devices 1
- Significant metallic hardware artifact on MRI 1
- Preoperative planning for hardware trajectory and osseous margin delineation 1
- MRI unavailable and urgent imaging needed for neurologic deficits 2
Important limitation: CT has low sensitivity (40-55%) for disc density evaluation and disc herniation detection compared to MRI. 4
Common Pitfalls to Avoid
Do NOT Order Imaging Without Meeting Criteria
Routine imaging in uncomplicated low back pain without 6 weeks of failed conservative therapy provides no clinical benefit and leads to increased healthcare utilization. 1 Many MRI abnormalities (disc degeneration, bulges) are seen in asymptomatic individuals and do not correlate with symptoms. 1, 5
Do NOT Start with Plain Radiographs
Plain X-rays cannot visualize discs, nerve roots, or the spinal canal adequately and will only delay appropriate diagnosis. 2 While radiographs may be complementary for assessing spondylolisthesis motion or axial loading, they are insufficient alone for surgical planning. 1
Do NOT Add IV Contrast Routinely
MRI without contrast is sufficient for evaluating radiculopathy and disc herniation. 2 Contrast should be reserved for suspected infection, malignancy, or postoperative evaluation. 2
Do NOT Delay Imaging When Neurologic Deficits Are Present
The standard recommendation against routine imaging in acute low back pain does not apply when motor weakness or other red flags are present. 2 Delayed diagnosis of neurologic deficits is associated with poorer outcomes and potential permanent disability. 2
Additional Considerations for Complex Cases
CT myelography can assess spinal canal patency and neural foramina when MRI is contraindicated, but requires lumbar puncture for intrathecal contrast injection. 1
SPECT/CT bone scan may help identify facet arthropathy or sacroiliac joint dysfunction as pain generators in select cases, though evidence is limited. 1