Overview
Necrotising Fasciitis
Topic Overview
Summary
Necrotising fasciitis (NF) is a rapidly progressive, life-threatening soft tissue infection involving necrosis of subcutaneous tissue and fascia. It spreads along fascial planes and can cause death within hours. Classic features include pain out of proportion to clinical findings, rapidly spreading cellulitis, and systemic toxicity. Risk factors include diabetes, immunocompromise, and recent trauma or surgery. Treatment is emergency surgery (debridement) plus IV antibiotics. Mortality is 20-40% even with treatment.
Key Facts
- Mortality: 20-40% (higher if delayed surgery)
- Key feature: Pain OUT OF PROPORTION to examination findings
- Classification: Type I (polymicrobial), Type II (Group A Strep), Type III (Clostridial gas gangrene)
- Treatment: EMERGENCY surgical debridement + IV antibiotics + ICU
- Fournier's gangrene: Necrotising fasciitis of perineum/genitalia
Clinical Pearls
"Pain out of proportion" + fever + cellulitis = think necrotising fasciitis
Do NOT wait for crepitus or skin necrosis — these are LATE signs
Surgical debridement is life-saving — do not delay for imaging
Why This Matters Clinically
Necrotising fasciitis kills rapidly. Early recognition, immediate surgical debridement, and broad-spectrum antibiotics are life-saving. Every hour of delay increases mortality.
Visual Summary
Visual assets to be added:
- Necrotising fasciitis clinical photos
- CT showing gas in soft tissues
- LRINEC score table
- Management algorithm
Epidemiology
Incidence
- 0.4-1 per 100,000/year
- Increasing due to more immunocompromised patients
Demographics
- All ages
- Male predominance
- Higher in diabetics, immunocompromised
Risk Factors
| Factor | Notes |
|---|---|
| Diabetes mellitus | Most common risk factor |
| Immunocompromise | HIV, chemotherapy, steroids |
| Obesity | |
| IV drug use | |
| Recent trauma/surgery | Entry point for bacteria |
| Peripheral vascular disease | |
| Chronic liver/renal disease |
Pathophysiology
Mechanism
- Bacteria enter through break in skin/mucosa
- Infection spreads along fascial planes
- Thrombosis of blood vessels → tissue ischaemia
- Necrosis of fascia and subcutaneous tissue
- Systemic toxicity (toxins, inflammatory response)
Classification
| Type | Organisms | Notes |
|---|---|---|
| Type I | Polymicrobial (anaerobes + aerobes) | Most common; diabetics, perineum |
| Type II | Group A Streptococcus (± S. aureus) | Previously healthy; rapid; high mortality |
| Type III | Clostridial (gas gangrene) | Trauma; gas in tissues |
Why Pain Out of Proportion
- Nerve ischaemia due to thrombosis
- Deep tissue destruction before skin changes
Clinical Presentation
Early Signs (May Be Subtle)
Late Signs (Do Not Wait For These)
Specific Types
| Type | Location |
|---|---|
| Fournier's gangrene | Perineum, genitalia |
| Cervical | Neck (often dental origin) |
| Limb | Upper or lower extremity |
| Abdominal wall | Post-operative |
Red Flags
| Finding | Significance |
|---|---|
| Pain out of proportion | Early key sign |
| Rapidly spreading erythema | Despite antibiotics |
| Blistering/necrosis | Late — needs immediate surgery |
| Crepitus | Gas-forming organisms |
| Septic shock | Very high mortality |
Pain out of proportion to clinical findings — key feature
Common presentation.
Erythema, swelling
Common presentation.
Fever, tachycardia
Common presentation.
Tenderness extending beyond visible erythema
Common presentation.
Clinical Examination
General
- Toxic, unwell
- Fever or hypothermia
- Tachycardia, hypotension
Local
- Erythema with ill-defined margins
- Tenderness extending beyond erythema
- Swelling, induration
- Blistering (haemorrhagic)
- Skin necrosis
- Crepitus (late)
Probe Test
- If skin breaks down, probe can pass along fascial planes (intraoperative)
Investigations
Blood Tests
| Test | Finding |
|---|---|
| WCC | Often very high (over 25) or low |
| CRP | Markedly elevated |
| Sodium | Often low (under 135) |
| Creatinine | Often elevated |
| Glucose | Often elevated |
| Lactate | Elevated (sepsis) |
| CK | May be elevated (muscle involvement) |
| Blood cultures | Essential |
LRINEC Score (Laboratory Risk Indicator for NF)
| Parameter | Points |
|---|---|
| CRP over 150 | 4 |
| WCC over 25 | 2 |
| Hb under 110 | 2 |
| Na under 135 | 2 |
| Creatinine over 141 | 2 |
| Glucose over 10 | 1 |
- Score 6 or more: Suspect NF
- Score 8 or more: High risk
Imaging
| Modality | Findings |
|---|---|
| CT | Gas in soft tissues; fascial thickening; fluid tracking |
| MRI | Most sensitive but delays surgery |
| X-ray | May show subcutaneous gas |
IMPORTANT: Do NOT delay surgery for imaging if clinical suspicion is high.
Classification & Staging
By Microbiology
| Type | Organisms |
|---|---|
| Type I | Polymicrobial |
| Type II | Monomicrobial (GAS, S. aureus) |
| Type III | Clostridial |
By Anatomical Site
- Limb
- Perineal (Fournier's)
- Cervical
- Abdominal wall
Management
Immediate — Resuscitation
| Action | Details |
|---|---|
| IV access | Large bore |
| IV fluids | Aggressive resuscitation |
| Blood cultures | Before antibiotics if possible |
| Alert surgical team | URGENT |
| ICU referral | Often needed |
IV Antibiotics — Broad-Spectrum
| Regimen | Notes |
|---|---|
| Piperacillin-tazobactam | Broad-spectrum |
| + Clindamycin | Toxin inhibition (GAS) |
| + Vancomycin | If MRSA risk |
| Or Meropenem + clindamycin | Alternative |
Surgery — EMERGENCY Debridement
| Principle | Details |
|---|---|
| Timing | URGENT — do not delay |
| Extent | Excise all necrotic tissue |
| Re-look | Planned return to theatre in 24-48h |
| Repeat debridement | Until healthy tissue |
| Amputation | May be necessary for limb NF |
Supportive Care
- ICU for organ support
- Vasopressors if needed
- Renal replacement therapy
- Nutrition
Adjuncts
- IV immunoglobulin (IVIG) — for streptococcal toxic shock
- Hyperbaric oxygen — controversial, limited evidence
Complications
Local
- Extensive tissue loss
- Limb loss (amputation)
- Disfigurement
Systemic
- Septic shock
- Multi-organ failure
- DIC
- Death (20-40%)
Long-Term
- Scarring
- Functional impairment
- PTSD
Prognosis & Outcomes
Mortality
- Overall: 20-40%
- Higher with delayed surgery, older age, comorbidities
Factors Affecting Outcome
- Time to surgery (most important)
- Extent of infection
- Organism (Type II GAS can be rapidly fatal)
- Patient comorbidities
Evidence & Guidelines
Key Guidelines
- No specific national guideline
- Management based on case series and expert consensus
Key Evidence
- Early surgical debridement reduces mortality
- Clindamycin reduces toxin production in GAS
Patient & Family Information
What is Necrotising Fasciitis?
Necrotising fasciitis is a very serious infection that spreads rapidly under the skin. It needs emergency surgery.
Symptoms
- Severe pain that seems out of proportion
- Rapidly spreading redness
- Fever and feeling very unwell
- Blistering or black skin (later)
Treatment
- Emergency surgery to remove infected tissue
- Strong antibiotics
- Intensive care
Outcome
- This is a life-threatening condition
- Some people need multiple operations
- Some may need amputation
Resources
References
Key Reviews
- Stevens DL, Bryant AE. Necrotizing Soft-Tissue Infections. N Engl J Med. 2017;377(23):2253-2265. PMID: 29211672
- Hakkarainen TW, et al. Necrotizing soft tissue infections: review and current concepts in treatment, systems of care, and outcomes. Curr Probl Surg. 2014;51(8):344-362. PMID: 25069713
LRINEC Score
- Wong CH, et al. The LRINEC (Laboratory Risk Indicator for Necrotizing Fasciitis) score: a tool for distinguishing necrotizing fasciitis from other soft tissue infections. Crit Care Med. 2004;32(7):1535-1541. PMID: 15241098