Necrotising Fasciitis
Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management
Definition
Necrotising fasciitis is a rapidly progressing soft tissue infection causing necrosis of the fascia and surrounding tissues, often leading to sepsis and multi organ failure if not treated promptly.
Aetiology
- Type 1 (polymicrobial): commonly involves Gram-positive, Gram-negative, and anaerobic bacteria (e.g., Streptococcus, Staphylococcus, Enterobacteriaceae, Clostridium).
- Type 2 (monomicrobial): usually caused by Group A Streptococcus (GAS) or Staphylococcus aureus.
- Type 3: caused by marine Vibrio species, typically from seawater exposure.
- Type 4: fungal necrotising fasciitis, rare but associated with immunosuppression.
Pathophysiology
- Bacteria invade deep soft tissues, releasing toxins that cause tissue necrosis.
- Rapid spread along fascial planes leads to severe systemic inflammation.
- Microvascular thrombosis results in tissue ischaemia and further necrosis.
- Systemic toxin release leads to septic shock and multi-organ failure.
Risk Factors
- Diabetes mellitus.
- Immunosuppression (chemotherapy, HIV, steroid use).
- Recent trauma, surgery, or deep penetrating injuries.
- Intravenous drug use.
- Peripheral vascular disease.
- Obesity.
Signs and Symptoms
- Severe pain disproportionate to physical findings.
- Rapidly spreading erythema, swelling, and tenderness.
- Skin changes: blistering, dusky or purplish discolouration, crepitus.
- Systemic symptoms: fever, tachycardia, hypotension, confusion.
- Skin necrosis and bullae in advanced stages.
Investigations
- Full blood count (FBC): leukocytosis with raised neutrophils.
- Inflammatory markers: markedly elevated CRP and ESR.
- Renal function and lactate: assesses severity of sepsis.
- Blood cultures: to identify causative organisms.
- Imaging: X-ray or CT may show gas in soft tissues; MRI is most sensitive.
- Surgical exploration: definitive diagnosis based on direct visualisation of necrotic fascia.
Management
1. Immediate Resuscitation:
- Administer broad-spectrum IV antibiotics (follow local guideline).
- Urgent surgical debridement – often requires multiple procedures.
- IV fluid resuscitation for septic shock.
- Analgesia and supportive care in a critical care setting.
2. Ongoing Management:
- Further debridement and wound care as required.
- Consider hyperbaric oxygen therapy in select cases.
- Nutrition support and intensive monitoring in an ICU setting.
3. Referral:
- Emergency surgery: for immediate debridement.
- Intensive care: for patients with septic shock.
- Infectious diseases: for prolonged antibiotic therapy and microbiological input.