Epidemiology
Etiology
Routes of infection
- Hematogenous spread from a distant focus (e.g., skin and soft tissue infection, urinary tract infection)
- Direct inoculation (e.g., during spinal surgery or due to trauma)
- Contiguous spread from adjacent infections (e.g., aorta, esophagus)
Pathogens
Risk factors
- Age > 50 years
- Sickle cell disease
- Immunocompromise: e.g., steroid use, HIV infection
- Intravenous drug use
- Recent bacteremia
- Infective endocarditis
- Recent spinal surgery and instrumentation
- Intravascular devices
- Malnutrition
- Chronic medical conditions:
Pathophysiology
Clinical features
Diagnostics
- Initial / Screening:
- ESR and CRP: Markedly elevated in >90% of cases; highly sensitive screening tools; used to monitor treatment response.
- CBC: Leukocytosis with left shift (frequently normal in chronic cases).
- Blood Cultures (x2 sets): Positive in up to 50-70%; can identify pathogen and avoid invasive biopsy.
- Confirmatory / Imaging of Choice:
- MRI spine with and without IV contrast: Gold standard (high sensitivity/specificity).
- Shows disc space narrowing, fluid collection, bone marrow edema, and epidural space enhancement.
- Alternative (if MRI contraindicated due to metal/pacemaker): CT spine with IV contrast or CT myelography.
- Plain Radiographs: Low sensitivity in early infection; requires 2-4 weeks to show disc space narrowing and endplate erosion.
- Biopsy / Microbiological Confirmation:
- CT-guided percutaneous needle aspiration/biopsy: Indicated if blood cultures are negative and MRI is abnormal.
- Rule: Hold empiric Abx prior to biopsy unless the patient is hemodynamically unstable or has progressive neurologic deficits.
Treatment