What are the criteria to send someone to the Emergency Room (ER) with lower back pain?

Emergency Room Criteria for Lower Back Pain

Send patients to the ER immediately if they present with cauda equina syndrome, rapidly progressive neurologic deficits, or signs of serious infection or malignancy—these are true emergencies requiring urgent imaging and intervention. 1

Red Flags Requiring Emergency Evaluation

Immediate ER Referral (True Emergencies)

Cauda equina syndrome is the most critical red flag and requires urgent MRI within hours 1:

• Urinary retention (90% sensitivity for cauda equina syndrome) 1
• New-onset bowel or bladder incontinence 1, 2
• Saddle anesthesia (numbness in perianal/perineal region) 1, 2
• Bilateral lower extremity weakness or motor deficits at multiple levels 1, 2
• Loss of anal sphincter tone 2

Progressive or severe neurologic deficits warrant immediate evaluation 1:

• Major motor weakness that is worsening 2
• Progressive sensory deficits 2
• Multiple nerve root involvement 1

High-Priority ER Referral (Serious Underlying Pathology)

Suspected spinal infection requires urgent evaluation 1:

• Fever with back pain 1, 3
• History of intravenous drug use 1
• Recent infection (especially urinary tract, respiratory, or skin infections) 1
• Immunosuppression 1
• Intense localized pain with inability to find comfortable position 3

Suspected malignancy should prompt urgent workup 1:

• History of cancer (increases probability from 0.7% to 9%) 1
• Age over 50 years with new-onset back pain 1
• Unexplained weight loss 1, 3
• Failure to improve after one month of conservative treatment 1
• Severe nighttime pain that awakens patient 1

Significant trauma-related fracture risk requires immediate imaging 1, 2:

• Major trauma in younger patients (fall from height, motor vehicle crash) 2
• Minor trauma in elderly or those with osteoporosis risk 2
• History of prolonged corticosteroid use 1, 3
• Age over 70 years 1

Common Pitfalls to Avoid

Do not send patients to the ER for uncomplicated acute low back pain (<4 weeks duration) without red flags—this is a self-limited condition that responds to conservative management in 90% of cases 1. Routine imaging provides no clinical benefit and leads to increased healthcare utilization without improved outcomes 1.

Urinary retention is key: In patients without urinary retention, the probability of cauda equina syndrome drops to approximately 1 in 10,000 1. However, maintain high clinical suspicion as diagnosis is frequently delayed in 15-41% of cases 1.

Radicular pain alone is not an emergency: Sciatica or leg pain radiating below the knee, even with positive straight-leg raise test, does not require ER evaluation unless accompanied by progressive motor weakness or cauda equina symptoms 1.

Clinical Decision Algorithm

1. Assess for cauda equina syndrome first: Ask specifically about urinary retention, bowel incontinence, and saddle anesthesia 1

2. Evaluate neurologic function: Test motor strength (knee extension for L4, great toe dorsiflexion for L5, ankle plantarflexion for S1), reflexes, and sensory distribution 1

3. Screen for infection: Check for fever, recent infections, IV drug use, or immunosuppression 1, 3

4. Assess cancer risk: History of cancer, age >50, unexplained weight loss, or night pain 1

5. Evaluate trauma and fracture risk: Mechanism of injury relative to patient age and bone health 2

If any red flags are present, send to ER immediately for urgent MRI and specialist evaluation 1. Without red flags, manage conservatively in outpatient setting with reassurance, activity modification, and simple analgesics 1.