A patient with a history of low back injury 10 years prior, presents with severe low back pain, left greater than right, that began 2 days ago, worsens when standing erect, and radiates to both thighs, what is the most likely diagnosis and recommended management for this patient?

Most Likely Diagnosis: Lumbar Radiculopathy (Sciatica)

This patient most likely has lumbar radiculopathy from disc herniation at L4/L5 or L5/S1, given the severe pain radiating bilaterally to the thighs, relief with forward flexion (which increases spinal canal diameter), and worsening with erect posture (which narrows the canal). 1

Diagnostic Classification

This presentation fits into the second category of low back pain: back pain potentially associated with radiculopathy or spinal stenosis, rather than nonspecific low back pain. 1 The key distinguishing features are:

• Bilateral thigh radiation suggests nerve root involvement, though more than 90% of symptomatic disc herniations occur at L4/L5 and L5/S1 levels 1
• Positional relief with forward flexion is characteristic of spinal stenosis or radiculopathy, as this position increases available space for neural structures 2
• Worsening with erect posture further supports mechanical compression of nerve roots 2

Critical Red Flag Assessment

You must immediately rule out cauda equina syndrome, which has an estimated prevalence of 0.04% in low back pain patients but requires urgent intervention. 1 Specifically assess for:

• Urinary retention (90% sensitivity for cauda equina syndrome) - the patient denies urinary symptoms, which reduces probability to approximately 1 in 10,000 1
• Fecal incontinence or loss of anal sphincter tone 1
• Saddle anesthesia 3
• Progressive motor deficits at multiple levels 1

Since the patient has no urinary symptoms, no fever, and no progressive neurologic deficits, cauda equina syndrome and infection are unlikely. 1, 2

Physical Examination Requirements

Perform a focused neurologic examination including:

• Straight-leg-raise test (91% sensitivity for herniated disc when positive between 30-70 degrees of leg elevation) 1
• Crossed straight-leg-raise test (88% specificity but only 29% sensitivity) 1
• Motor strength testing: knee strength (L4), great toe/foot dorsiflexion (L5), foot plantarflexion (S1) 1
• Reflex testing: knee reflexes (L4), ankle reflexes (S1) 1
• Sensory distribution in dermatomal patterns 2

Imaging Decision

Do NOT obtain routine imaging at this initial ER visit. 1, 2 The American College of Physicians strongly recommends against routine imaging in patients without red flags. 1

However, if severe or progressive neurologic deficits are found on examination, obtain urgent MRI (preferred over CT for superior soft tissue visualization). 1, 2, 4

For this patient with severe pain but no red flags, the imaging algorithm is:

• No imaging now - initiate conservative management 1, 5
• Consider MRI after 4-6 weeks if symptoms persist despite conservative treatment 4, 5
• Earlier MRI (within 2 weeks) if pain remains severe and disabling despite treatment 2

Acute Pain Management

Initiate NSAIDs as first-line therapy - they are 10 points more effective than acetaminophen on a 100-point visual analogue scale. 2, 6

If NSAIDs are insufficient for this severe pain:

• Consider short-term opioids or tramadol for severe, disabling pain, carefully weighing benefits versus risks 2
• Avoid bed rest - it worsens outcomes 6, 3
• Acetaminophen has little evidence of benefit for mechanical low back pain 6, 7

Disposition and Follow-Up

Discharge with close outpatient follow-up in 1-2 weeks given the severity of symptoms. 2 The American College of Physicians recommends:

• Earlier reevaluation (not waiting the standard 1 month) for patients with severe pain, functional deficits, or signs of radiculopathy 2
• Specialist referral within 2 weeks if pain remains severe or disabling despite initial management 2
• Return precautions for development of urinary retention, saddle anesthesia, progressive weakness, or fecal incontinence 1

Common Pitfalls to Avoid

• Do not order MRI in the ER unless red flags are present - this leads to identification of radiographic abnormalities poorly correlated with symptoms and potentially unnecessary interventions 1
• Do not prescribe muscle relaxants - evidence of benefit is lacking for chronic low back pain 6, 7
• Do not recommend bed rest - patients should remain as active as tolerated 6, 3
• Do not miss cauda equina syndrome - always ask specifically about urinary retention, the most sensitive finding 1, 2

Psychosocial Assessment

Screen for psychosocial factors that predict poorer outcomes, including depression, passive coping strategies, job dissatisfaction, and disputed compensation claims. 1 These factors are stronger predictors of outcomes than physical findings and should guide intensity of follow-up. 2