From the Guidelines
For a patient with excruciating right low back and leg pain who can barely walk, I recommend ordering an MRI of the lumbar spine as the primary diagnostic test. This non-invasive imaging study will provide detailed visualization of the spinal cord, nerve roots, intervertebral discs, and surrounding structures to identify potential causes such as disc herniation, spinal stenosis, or nerve root compression, as suggested by the American College of Radiology in their 2021 update 1.
While waiting for the MRI, consider ordering plain X-rays of the lumbar spine to rule out obvious bony abnormalities like fractures or severe degenerative changes. Laboratory tests including complete blood count, C-reactive protein, and erythrocyte sedimentation rate would help identify infectious or inflammatory processes. The patient's symptoms suggest possible sciatica or radiculopathy, which typically results from compression of nerve roots in the lumbar spine. The inability to walk indicates severe pain or possibly neurological compromise, making prompt evaluation essential.
Some key points to consider when evaluating this patient include:
- The natural history of lumbar disc herniation with radiculopathy in most patients is for improvement within the first 4 weeks with noninvasive management, as noted in the American College of Physicians and the American Pain Society joint clinical practice guideline 1.
- MRI has excellent soft-tissue contrast and accurately depicts lumbar pathology, including disc degeneration, as well as the thecal sac and neural structures, making it the preferred initial imaging modality for patients with subacute or chronic low back pain who have failed conservative therapy 1.
- If there are any red flags such as bowel or bladder dysfunction, saddle anesthesia, or progressive neurological deficits, an emergency MRI should be ordered as these symptoms may indicate cauda equina syndrome requiring immediate surgical intervention.
It's also important to note that findings on MRI or CT, such as bulging disc without nerve root impingement, are often nonspecific, and decisions should be based on the clinical correlation between symptoms and radiographic findings, severity of symptoms, patient preferences, surgical risks, and costs, as recommended by the American College of Physicians and the American Pain Society joint clinical practice guideline 1.
From the Research
Diagnostic Tests for Low Back and Leg Pain
The patient's symptoms of excruciating right low back and leg pain and difficulty walking suggest a possible lumbar disc herniation or spinal stenosis.
- To diagnose these conditions, the following tests can be considered:
- Magnetic Resonance Imaging (MRI): MRI is a highly sensitive and specific test for diagnosing lumbar disc herniation, with a sensitivity of 91.7% and specificity of 100% 2.
- Electrodiagnostic study (EDX): EDX can also be used to diagnose lumbar disc herniation or spinal stenosis, and has been shown to have a higher specificity than MRI in terms of physical examination data 3.
- Computed Tomography (CT) scan: While CT scans can be used to diagnose lumbar disc herniation, they have been shown to be less accurate than MRI, with a sensitivity of 83.3% and specificity of 71.4% 2.
Test Selection
Based on the patient's symptoms, an MRI or EDX may be the most appropriate initial test.
- MRI is a non-invasive test that can provide detailed images of the lumbar spine and discs, and can help to diagnose lumbar disc herniation or spinal stenosis.
- EDX can provide information about the electrical activity of the muscles and nerves, and can help to diagnose radiculopathy or other conditions that may be causing the patient's symptoms.
- A CT scan may be considered if the MRI or EDX results are equivocal or if further imaging is needed to clarify the diagnosis.
Note: The study 4 is not relevant to the diagnosis of low back and leg pain, as it discusses histidine transport in the Ehrlich cell.