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Back Pain: Red Flags & Differential Diagnosis

Family Medicine Year 3 Presentation

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1. Overview

1. Nonspecific (mechanical) back pain — most common (~85%)
2. Radicular pain — nerve root involvement
3. Red flag–associated symptoms — serious underlying pathology

"Clinicians find red flag clues useful as simple ways to reassure themselves and their patients that a common symptom such as back pain does not have a sinister cause." — Harrison's Principles of Internal Medicine 22E

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2. Evaluation Approach

• No red flags → Conservative management; imaging NOT indicated before 6 weeks
• Red flags present → Urgent MRI or specialist referral

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3. Red Flags — By Serious Condition

🔴 Cauda Equina Syndrome (SURGICAL EMERGENCY)

Requires same-day emergency MRI and neurosurgical referral.

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🔴 Spinal Fracture

• Sudden severe central spinal pain relieved by lying down
• History of major trauma (RTC, fall from height)
• Minor trauma or lifting in osteoporosis or steroid use
• Structural deformity or step deformity on palpation
• Point tenderness over vertebral body

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🔴 Malignancy (Primary or Metastatic)

• Age >50 years
• Gradual onset of worsening pain
• Unremitting pain present at rest/supine and at night (disturbs sleep)
• Pain aggravated by Valsalva (coughing, sneezing, straining at stool)
• Thoracic back pain (unusual distribution)
• Localised spinal tenderness
• Unexplained weight loss
• No improvement after 4–6 weeks of conservative therapy
• History of cancer — especially breast, lung, GI, prostate, renal, thyroid (all metastasise to spine)

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🔴 Spinal Infection (Discitis, Vertebral Osteomyelitis, Epidural Abscess)

• Fever
• History of TB or recent UTI
• Diabetes mellitus
• IV drug use
• HIV / immunosuppression / immunocompromise
• Recent spinal surgery

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🔴 Other High-Risk Red Flags (Goldman-Cecil Table 369-3)

"Back pain in a child is a red flag for serious spinal pathology." — Bailey & Love's Surgery 28E

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4. Differential Diagnosis of Back Pain

Organised by Category

Key point: AAA classically presents as severe, tearing back/flank pain in an older patient — do not miss this vascular emergency.

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5. Clinical Clues at a Glance

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6. Key Examination Tests

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7. When to Image

Radiographs require 40–60% bone destruction before detecting infection or tumour — not adequate for ruling out serious pathology. — Bailey & Love's Surgery 28E

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8. Summary Memory Aid — RED FLAGS Mnemonic

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Back Pain: Red Flags & Differential Diagnosis

Family Medicine | MBBS Year 3 | ~8 min presentation

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Who Presents with Back Pain?

• Extremely common — one of the top reasons patients visit a GP
• 85% is mechanical (muscle strain, disc, posture) — benign, self-limiting
• 15% has a serious cause — your job is to not miss this 15%

The clinical task = screen for red flags first, then manage the rest

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The 3-Category Framework

Back Pain
    │
    ├── 1. Nonspecific / Mechanical   ← most common, treat conservatively
    ├── 2. Radicular (nerve root)     ← sciatica, disc herniation
    └── 3. RED FLAG conditions        ← serious, must rule out first

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RED FLAGS — The 4 Dangerous Causes

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🔴 1. Cancer (Metastatic Spine)

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🔴 2. Infection (Osteomyelitis / Epidural Abscess / Discitis)

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🔴 3. Fracture

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🔴 4. Cauda Equina Syndrome — ⚠️ SURGICAL EMERGENCY

Miss this = permanent paralysis / incontinence

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Quick Red Flag Summary Table

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Differential Diagnosis — Simplified

Clinical clue shortcuts:

• Young man + morning stiffness + improves with exercise → Ankylosing spondylitis
• Pain radiating below knee + positive SLR → Disc herniation / Sciatica
• Leg pain on walking + relieved by leaning forward → Spinal stenosis
• Colicky flank pain → groin → testis + haematuria → Renal colic (referred)
• Pulsatile abdominal mass + tearing back pain → AAA — call surgeon NOW

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When to Image?

X-rays miss early cancer and infection (need 40–60% bone destruction first) — MRI is the investigation of choice

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Evaluation Flowchart

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Take-Home Messages (Say These in Your Conclusion)

1. Most back pain is mechanical — reassure and treat conservatively
2. Always screen for red flags — CIFS: Cancer, Infection, Fracture, cauda equina Syndrome
3. Cauda equina = emergency — saddle anaesthesia + bladder/bowel = call surgeon today
4. Night pain + weight loss + age >50 = cancer until proven otherwise
5. No imaging before 6 weeks unless red flags are present
6. Don't forget referred pain — kidney, aorta, pancreas can all present as back pain

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References

Textbooks

1. Rakel, R.E. & Rakel, D.P. — Textbook of Family Medicine, 9th Edition. Elsevier Saunders.
   • Chapter 31: Chronic Low Back Pain — Diagnostic approach, red flag classification, imaging guidelines
2. Goldman, L. & Schafer, A.I. — Goldman-Cecil Medicine, International Edition (2 Vol. Set). Elsevier.
   • Table 369-3: Red Flags in the Evaluation of Spine Pain
   • Evaluation flowchart for acute and subacute neck and low back pain
3. Williams, N.S., O'Connell, P.R. & McCaskie, A.W. — Bailey and Love's Short Practice of Surgery, 28th Edition. CRC Press/Taylor & Francis.
   • Table 37.5: Red flags — serious conditions causing low back pain
   • Table 37.6: Non-spinal (referred) causes of low back pain
   • Summary box 44.17 & 44.18: Red flag symptoms and signs for spinal pathology
4. Blumenfeld, H. — Neuroanatomy through Clinical Cases, 3rd Edition. Sinauer/Oxford University Press.
   • Table 8.2: Differential Diagnosis of Back Pain (organised by pathological category)
5. Kasper, D.L. et al. — Harrison's Principles of Internal Medicine, 22nd Edition (2025). McGraw-Hill Medical.
   • Differential diagnosis of mechanical vs. pathological back pain; red flag clues in clinical context

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Guidelines Referenced (within textbook content)

• American College of Physicians (ACP) / American Pain Society — Joint 2007 guideline on low back pain: three-category classification framework (nonspecific, radicular, red flag)
• NICE (UK National Institute for Health and Care Excellence) — Guidelines on chronic low back pain management (2009): evidence base for physiotherapy, manual therapy, and conservative care

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For Further Reading

• Chou R, et al. Diagnosis and treatment of low back pain: a joint clinical practice guideline from the ACP and APS. Ann Intern Med. 2007;147(7):478–491.
• NICE guideline NG59: Low back pain and sciatica in over 16s. Updated 2020. nice.org.uk/guidance/ng59