🔑 Key Learning

  • Discitis = infection of the intervertebral disc space, most commonly caused by Staphylococcus aureus.
  • Presents with back pain, fever, and raised inflammatory markers.
  • Most commonly affects the lumbar spine.
  • MRI is the investigation of choice.
  • Treat with IV antibiotics, surgical debridement if needed.

🧬 Pathophysiology

  • Infection of the intervertebral disc
  • Staphylococcus aureus is the most common organism
  • Other possible organisms: Gram negatives, Mycobacterium tuberculosis (in endemic areas or immunocompromised)
  • Usually spreads via haematogenous seeding
  • Most often involves the lumbar region

👀 Clinical Features

  • Localised back pain at the affected disc level
  • Fever, malaise, and systemic symptoms
  • Weight loss
  • Neurological signs (e.g. limb weakness, radiculopathy) 
  • History may include recent infection, IVDU, or immunosuppression

🧪 Investigations

  • Bloods:
    • ↑ CRP / ESR
    • ↑ WCC
  • Blood cultures – to isolate causative organism- often staph aureus
  • MRI spine – gold standard (high sensitivity and specificity)
  • Disc space biopsy – for culture and histology if diagnosis uncertain

💊 Management

  • IV antibiotics
    • Empirical cover for Staph aureus: e.g. flucloxacillin
    • Clindamycin or vancomycin in penicillin-allergic or MRSA-risk patients
  • Tailor antibiotics based on culture results
  • Duration: usually 6 weeks or more of IV therapy
  • Surgical intervention
    • Reserved for failure of medical therapy, spinal instability, or abscess formation

📝 Exam Clues & Clinchers

  • Back pain + fever + raised CRP + IVDU/diabetes → consider discitis → MRI spine