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Necrotising soft-tissue infection (necrotising fasciitis and Fournier's)
Necrotising soft-tissue infection is a surgical emergency: pain out of proportion to the skin appearance and rapid deterioration require surgical debridement within hours, with broad antibiotics that include clindamycin — imaging and laboratory tests do not replace the clinical decision.
Why it matters in the exam
The typical case is a diabetic patient, after minor trauma or surgery, with very severe pain relative to modest redness, rapidly spreading swelling, bullae, dark insensate areas, crepitus and signs of sepsis. The exam checks that you understand the infection spreads along the fascia beneath relatively normal-looking skin, so the decision is clinical: the LRINEC score or CT showing gas in the tissues can support it, but a normal result does not exclude it, and surgery must not be delayed because of them.
Candidates are also asked about the types: type I polymicrobial (diabetes, after surgery, Fournier's in the perineum), type II from group A streptococcus (sometimes with toxic shock syndrome, even in healthy young people), clostridial gas gangrene after a deep wound, and Vibrio vulnificus after seawater exposure in a patient with liver disease. Treatment: extensive debridement to healthy tissue, return to theatre within 24–48 hours, and broad antibiotics — a carbapenem or piperacillin-tazobactam, together with vancomycin and clindamycin to suppress toxin production.
Key points
- Pain out of proportion, rapid spread, bullae, crepitus — suspect necrotising infection.
- The decision is clinical; surgical debridement within hours.
- Return to theatre within 24–48 hours.
- Antibiotics: a carbapenem or piperacillin-tazobactam, with vancomycin and clindamycin.
- Fournier's — necrotising infection of the perineum.
Summary table
| Type | Background | Features | Treatment in addition to debridement |
|---|---|---|---|
| Type I (polymicrobial) | Diabetes, after surgery, perineum (Fournier's) | Aerobic and anaerobic bacteria | Broad antibiotics; in the perineum — sometimes a diverting stoma |
| Type II (group A streptococcus) | Even a healthy young person, after minor trauma | Rapid progression, sometimes toxic shock | Clindamycin; consider IVIG in toxic shock |
| Gas gangrene (Clostridium) | Deep, contaminated or traumatic wound | Crepitus, gas on CT, dishwater discharge | Extensive debridement, sometimes amputation |
| Vibrio vulnificus | Seawater exposure, liver disease | Haemorrhagic bullae, rapid sepsis | Doxycycline with ceftazidime |
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Sources
- IDSA Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections, 2014 — Necrotising fasciitis and gas gangrene
- WSES/SIS-E guidelines for the management of skin and soft-tissue infections, 2018 — Diagnosis, debridement and antibiotic therapy
- Sabiston Textbook of Surgery, 21st edition (2022) — Surgical Infections and Antibiotic Use
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.