What tests and exams should be done for a patient presenting to the emergency room (ER) with back pain?

Emergency Department Evaluation of Back Pain

Initial Triage: Focused History and Physical Examination

Conduct a targeted history and physical examination to categorize patients into three groups: nonspecific low back pain, back pain with radiculopathy/spinal stenosis, or back pain with serious underlying pathology. 1

Critical Red Flags Requiring Immediate Investigation

Screen systematically for red flags that indicate serious pathology requiring urgent imaging and intervention:

Neurologic Red Flags:

• Progressive motor weakness or sensory deficits in lower extremities 1, 2
• Bladder, bowel, or sexual dysfunction (cauda equina syndrome) 1, 3
• Saddle anesthesia or perianal numbness 3
• Bilateral lower extremity weakness, sensory changes, or absent reflexes 3
• Abnormal gait or inability to bear weight 4, 2

Infectious/Inflammatory Red Flags:

• Fever with back pain 1, 2
• History of intravenous drug use 1
• Recent infection or invasive spinal procedure 5
• Morning stiffness with improvement on exercise 1, 2
• Tachycardia 2

Malignancy Red Flags:

• History of cancer (increases probability from 0.7% to 9%) 1
• Unexplained weight loss 1, 2
• Age older than 50 years 1
• Night pain or constant pain unrelieved by rest 4, 2
• Pain lasting more than 4 weeks without improvement 1, 2

Fracture Red Flags:

• History of significant trauma relative to age 5
• Older age with osteoporosis risk factors 1
• Chronic steroid use 1

Physical Examination Components

Perform a targeted neurologic examination including:

• Straight-leg-raise test (91% sensitivity for herniated disc when positive between 30-70 degrees) 1
• Crossed straight-leg-raise test (88% specificity for herniated disc) 1
• Knee strength and reflexes (L4 nerve root) 1
• Great toe and foot dorsiflexion strength (L5 nerve root) 1
• Foot plantarflexion and ankle reflexes (S1 nerve root) 1
• Sensory distribution testing 1
• Spinal palpation for tenderness over spinous processes 2
• Assessment of spinal curvature and alignment 2
• Evaluation for lymphadenopathy 2

Laboratory Testing

Do not routinely obtain laboratory tests for nonspecific low back pain without red flags. 1

When red flags are present, obtain:

• Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) for suspected infection or inflammatory disease 4
• Complete blood count (WBC ≥12,000 cells/mm³ predicts septic arthritis) 4
• ESR ≥40 mm/hour and CRP >2.0 mg/dL are predictive of infection 4

Imaging Algorithm

Nonspecific Low Back Pain (No Red Flags)

Do not obtain imaging or diagnostic tests in patients with nonspecific low back pain. 1 More than 85% of primary care patients have nonspecific low back pain that resolves within 4-6 weeks with conservative management. 1, 6

Red Flags Present

Obtain imaging when severe or progressive neurologic deficits are present or when serious underlying conditions are suspected based on history and physical examination. 1

Initial Imaging:

• Plain radiographs (frontal and lateral views only) of the symptomatic spinal region as first-line imaging 4, 2
• Radiographs identify fractures, spondylolysis, primary bone tumors, vertebral alignment abnormalities, and disc height changes 4
• Critical caveat: Negative radiographs do not exclude serious pathology 4, 2

Advanced Imaging - MRI Indications:

URGENT MRI (obtain immediately):

• Suspected cauda equina syndrome with bladder/bowel dysfunction 3
• Rapidly progressive motor weakness 3
• Suspected spinal cord compression from malignancy 3
• Suspected epidural abscess or vertebral osteomyelitis with fever 3
• Pediatric patients with constant pain and nighttime symptoms (25-30% have spinal neoplasm) 4

MRI after initial radiographs:

• Persistent radiculopathy or spinal stenosis symptoms in surgical candidates 1
• Suspected infection (MRI with and without IV contrast) 2, 3
• Suspected malignancy (MRI with and without IV contrast) 2, 3
• Persistent symptoms after 6 weeks of conservative therapy in surgical/interventional candidates 3
• Positive or concerning radiographs with high clinical suspicion 4

MRI protocol selection:

• MRI without IV contrast for suspected cauda equina syndrome, radiculopathy, or spinal stenosis 3
• MRI with and without IV contrast for suspected infection, malignancy, or inflammatory conditions 2, 3
• Complete spine MRI when multifocal disease is possible 4

Common Pitfalls to Avoid

• Do not image uncomplicated back pain before 6 weeks unless red flags are present, as most cases resolve with conservative management 3
• Do not assume negative radiographs exclude serious pathology - proceed to MRI if red flags persist 4, 2
• Do not delay MRI in patients with progressive neurologic deficits - delayed diagnosis worsens outcomes 3
• Do not continue physical therapy when red flags are present - undiagnosed malignancy can lead to pathologic fracture progression, and infection can progress to epidural abscess 3
• Do not obtain oblique radiographic views - they double radiation exposure without added diagnostic benefit 4

Disposition Based on Findings

Immediate intervention required:

• Cauda equina syndrome: urgent neurosurgical consultation 1, 3
• Epidural abscess or vertebral osteomyelitis: IV antibiotics targeting Staphylococcus aureus and orthopedic/infectious disease consultation 4
• Spinal cord compression from malignancy: urgent oncology and neurosurgery consultation 4

Outpatient management with close follow-up:

• Nonspecific low back pain: reassurance, activity modification, NSAIDs or acetaminophen, and return precautions for red flags 1
• Radiculopathy without progressive deficits: conservative management with follow-up in 4-6 weeks 1