Acute Soft Tissue Infection

1. Clinical Overview

Summary

Acute soft tissue infections (SSTIs) represent a spectrum of bacterial infections affecting the skin, subcutaneous tissue, fascia, and muscle. These range from superficial cellulitis, which responds well to antibiotics, to life-threatening necrotising fasciitis (NF), which requires urgent surgical debridement. The condition affects millions globally, with cellulitis accounting for approximately 2-3% of emergency department presentations. [1] Mortality ranges from less than 1% for simple cellulitis to 20-40% for necrotising soft tissue infections (NSTIs), particularly when diagnosis or surgical intervention is delayed beyond 24 hours. [2,3]

The critical clinical challenge is distinguishing uncomplicated cellulitis from necrotising infection. While cellulitis can be managed with antibiotics and supportive care, necrotising fasciitis requires urgent surgical debridement—often within hours—to prevent death. Pain out of proportion to clinical findings, rapid progression (visible hourly spread), systemic toxicity, and cutaneous findings such as bullae, crepitus, or necrosis are cardinal features that should trigger immediate surgical consultation. [4,5]

Early recognition, appropriate antimicrobial therapy, and—when indicated—aggressive surgical debridement are the cornerstones of management. The LRINEC (Laboratory Risk Indicator for Necrotising Fasciitis) score can assist in risk stratification but should not delay surgical exploration if clinical suspicion is high. [6] Understanding the microbiological differences between streptococcal and staphylococcal infections informs both empirical antibiotic selection and prognosis.

Key Facts

• Definition: Bacterial infection of skin and underlying soft tissues ranging from superficial to life-threatening deep infections
• Incidence: Cellulitis 24.6 per 1,000 person-years; NF 0.4 per 100,000 person-years [1,7]
• Mortality: Cellulitis less than 1%; necrotising fasciitis 20-40% [2,3]
• Peak age: All ages; NF more common in 50-70 years
• Critical features: Erythema, oedema, warmth, pain; red flags include pain out of proportion, crepitus, bullae, rapid progression
• Key investigations: Clinical diagnosis (cellulitis); bloods including LRINEC score, imaging (CT/MRI), surgical exploration (NF)
• First-line treatment: Antibiotics for cellulitis; urgent surgical debridement plus broad-spectrum antibiotics for NF

Clinical Pearls

"Pain out of proportion is necrotising fasciitis until proven otherwise" — This single clinical feature has the highest sensitivity for NF. If a patient reports severe pain that seems excessive for the visible skin changes, immediately escalate to senior review and surgical consultation. Do not wait for imaging. [4,5]

"The LRINEC score assists but does not exclude necrotising fasciitis" — A score ≥6 has 92% positive predictive value, but a low score does not rule out NF. Clinical judgement trumps scoring systems. If surgical concern exists, explore. [6,8]

"Rapid progression means operating theatre, not more antibiotics" — If infection spreads visibly over hours despite antibiotics, this is necrotising infection requiring debridement. Mark the borders with a pen and reassess hourly. [9]

"Fournier's gangrene is a urological emergency" — Necrotising fasciitis of the perineum and genitalia requires aggressive early debridement, often multiple procedures, and has mortality exceeding 20% even with optimal treatment. [10]

"Streptococcal vs staphylococcal: know the difference" — Group A Streptococcus (GAS) tends to cause rapidly progressive, toxin-mediated disease with high systemic toxicity. Staphylococcus aureus infections may be more localised but MRSA complicates treatment. Empirical therapy must cover both. [11,12]

Why This Matters Clinically

Soft tissue infections are among the most common surgical emergencies. While most cases are straightforward cellulitis managed medically, failure to recognise necrotising infection early results in preventable deaths and major morbidity including limb loss. Every clinician—from foundation doctor to consultant—must be able to differentiate simple from complex infection, initiate appropriate antibiotics, and know when to urgently involve surgery. The condition also represents a major source of litigation when diagnosis is delayed.

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2. Epidemiology

Incidence & Prevalence

Cellulitis and Erysipelas:

• Incidence: 24.6 per 1,000 person-years in the general population [1]
• Responsible for approximately 2-3% of emergency department attendances [1]
• Hospital admissions for cellulitis increased 30% between 1998 and 2018 in the UK [13]
• Recurrence rate: 8-20% within 3 years [14]

Necrotising Soft Tissue Infections:

• Incidence: 0.4 per 100,000 person-years (rare but life-threatening) [7]
• Accounts for less than 1% of hospital admissions for soft tissue infections but > 50% of infection-related mortality [2]
• Fournier's gangrene: 1.6 per 100,000 males; 0.1 per 100,000 females [10]

Demographics

Risk Factors

Non-Modifiable:

• Age > 60 years (immunosenescence) [15]
• Male sex (for necrotising infections) [7]
• Previous history of cellulitis (8-fold increased recurrence risk) [14]

Modifiable:

Common Microbiology

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3. Pathophysiology

Infection Mechanism

Step 1: Pathogen Entry

Bacteria gain access to subcutaneous tissues through:

• Skin breach: Trauma, surgical wounds, IV cannulation, injection drug use, insect bites, fungal infection (tinea pedis is a major portal for lower limb cellulitis) [1]
• Haematogenous spread: Rare, usually Staphylococcus aureus bacteraemia seeding tissue
• Direct extension: From adjacent infection (e.g., osteomyelitis, septic arthritis)

Step 2: Invasion and Proliferation

• Cellulitis (superficial): Bacteria multiply in dermis and subcutaneous tissue, triggering inflammatory response → vasodilation, increased vascular permeability → clinical erythema, oedema, warmth [1]
• Necrotising fasciitis (deep): Bacteria invade along fascial planes, producing:
  • "Exotoxins (e.g., streptococcal pyrogenic exotoxins, staphylococcal toxic shock syndrome toxin): Trigger massive cytokine release → systemic inflammatory response syndrome (SIRS), septic shock [11]"
  • "Enzymes (hyaluronidase, collagenase, lipase): Digest tissue, facilitate rapid spread [19]"
  • "Ischaemia: Thrombosis of perforating vessels → tissue necrosis → rapidly progressive gangrene [4]"

Step 3: Systemic Response

• Cytokine storm (TNF-α, IL-1, IL-6) → systemic inflammatory response
• Capillary leak → hypotension, organ hypoperfusion
• Coagulopathy → disseminated intravascular coagulation (DIC)
• Multi-organ dysfunction syndrome (MODS)

Step 4: Outcome Without Intervention

• Cellulitis: May self-limit if immune-competent, or progress to abscess, lymphangitis, bacteraemia
• Necrotising fasciitis: Inexorable progression to shock, multi-organ failure, death within 24-72 hours if not surgically debrided [2,3]

Classification of Soft Tissue Infections

Anatomical Classification (IDSA 2014) [21]

Microbiology Classification (Giuliano & Meleney)

Anatomical Subtype: Fournier's Gangrene

• Necrotising fasciitis of perineum, genitalia, and perianal region
• Typically polymicrobial (type I)
• Often originates from urogenital or anorectal source
• Requires aggressive early debridement, often multiple procedures
• Mortality 20-40% [10]

Molecular Pathophysiology: Streptococcal vs Staphylococcal

Group A Streptococcus (S. pyogenes)

Virulence Factors:

• M protein: Antiphagocytic, adhesion
• Streptolysin O and S: Haemolysins, cytotoxic
• Pyrogenic exotoxins (SpeA, SpeB, SpeC): Superantigens → massive T-cell activation → cytokine storm → toxic shock syndrome [11]
• Streptokinase, hyaluronidase, DNAses: Facilitate tissue invasion

Clinical Features:

• Rapid progression (visible hourly spread)
• Marked systemic toxicity (fever, tachycardia, hypotension)
• Streptococcal toxic shock syndrome (STSS) in 50% of NF cases [11]
• High mortality (30-40%) despite treatment

Antibiotic Susceptibility:

• Uniformly penicillin-sensitive
• Clindamycin recommended as adjunct (suppresses toxin production) [21]

Staphylococcus aureus (including MRSA)

Virulence Factors:

• Protein A: Binds IgG, evades opsonisation
• Panton-Valentine leukocidin (PVL): Cytotoxin (especially in CA-MRSA)
• Toxic shock syndrome toxin-1 (TSST-1): Superantigen
• Exfoliative toxins: Cause blistering (staphylococcal scalded skin syndrome)

Clinical Features:

• More localised infection initially (abscess formation common)
• Less fulminant systemic toxicity than GAS (but PVL+ strains can be aggressive)
• MRSA complicates empirical therapy [12]

Antibiotic Resistance:

• MRSA: resistant to β-lactams; requires glycopeptides (vancomycin, teicoplanin) or alternatives (linezolid, daptomycin)
• CA-MRSA: often community-acquired, PVL-producing, associated with skin abscesses [12]

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4. Clinical Presentation

Symptoms: The Patient's Story

Typical Presentation: Cellulitis

Primary Symptoms:

• Erythema: Spreading redness, often with defined border (especially erysipelas)
• Oedema: Swelling of affected area and limb
• Pain: Tenderness on palpation and movement
• Warmth: Affected area hot to touch

Systemic Symptoms (Variable):

• Fever (present in 30-50%) [1]
• Rigors (suggests bacteraemia)
• Malaise, myalgia

Associated Features:

• History of skin trauma, insect bite, fungal infection (tinea pedis)
• Previous episodes of cellulitis (recurrence common) [14]
• Lymphangitic spread (visible red streaks tracking proximally)

Typical Presentation: Necrotising Fasciitis

Cardinal Symptoms (Red Flag Features):

1. Pain out of proportion to clinical findings — Sensitivity 80-90% for NF [4,5]

   • Severe, unremitting pain not explained by visible skin changes
   • Analgesic requirement escalating
   • May paradoxically decrease as nerves necrose

2. Rapid progression — Visible hourly spread of erythema/necrosis [9]

   • Infection border advancing measurably over hours
   • Sudden deterioration

3. Systemic toxicity — SIRS, septic shock [2]

   • High fever or hypothermia
   • Tachycardia (> 120 bpm)
   • Hypotension
   • Altered mental state
   • Oliguria

Cutaneous Features (Late Signs):

• Bullae (haemorrhagic blisters): Indicate dermal ischaemia [4]
• Crepitus: Palpable gas in tissues (30-50% of NF, higher in type I) [7]
• Skin necrosis: Purple/black discolouration, insensate (late, indicates nerve death)
• "Dishwater" discharge: Thin, grey, foul-smelling fluid

History Points:

• Recent trauma (may be trivial: scratch, injection, muscle strain)
• Immunosuppression (diabetes, steroids, chemotherapy)
• Recent surgery (especially GI/urogenital)
• NSAID use (possibly associated with more aggressive streptococcal infection) [22]

Signs: What You Find

Vital Signs

General Appearance

• Cellulitis: Uncomfortable but well-appearing
• NF: Systemically unwell, "toxic" appearance, distressed, septic

Local Examination: Cellulitis

Local Examination: Necrotising Fasciitis

"Finger Test" (Surgical Exploration): Under LA or in theatre, incision to fascia; if NF, blunt finger dissection along fascial plane encounters no resistance (normally fascia adherent to muscle). Grey, dishwater fluid and non-bleeding, necrotic tissue confirm diagnosis. [23]

Red Flags for Necrotising Infection

[!CAUTION] Immediate Escalation to Senior Surgical Team if ANY:

• Pain out of proportion to clinical findings — Most sensitive sign [4,5]
• Rapid progression (hourly spread) — Mark borders, reassess; progression = theatre [9]
• Crepitus — Gas in tissues; pathognomonic [7]
• Bullae or skin necrosis — Late signs, very concerning [4]
• Systemic toxicity — SIRS, shock, altered mental state [2]
• Hypoaesthesia — Nerve involvement, deep infection [4]
• Immunocompromised host — Diabetes, steroids, chemotherapy, HIV [15,18]
• Post-operative (especially GI/urogenital surgery) — High index of suspicion [7]

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5. Clinical Examination

Structured Approach: ABCDE Assessment

A - Airway

• Usually patent in cellulitis
• May be compromised in NF with severe sepsis/shock or if cervical infection (Ludwig's angina)
• Action: Assess, secure if needed, involve anaesthetics if airway concern

B - Breathing

• Respiratory rate: tachypnoea (> 22/min) suggests SIRS or metabolic acidosis [2]
• SpO2: hypoxia suggests ARDS or severe sepsis
• Auscultation: usually clear; crackles may indicate pulmonary oedema (fluid resuscitation, sepsis)
• Action: Supplemental oxygen to maintain SpO2 > 94%; ABG if shock or tachypnoea

C - Circulation

• Heart rate: tachycardia (> 120 bpm) common in NF [2]
• Blood pressure: hypotension (less than 90 mmHg systolic) indicates septic shock
• Capillary refill time: > 2 seconds suggests poor perfusion
• Urine output: oliguria (less than 0.5 mL/kg/hr) indicates renal hypoperfusion
• Action: IV access (large-bore), fluid resuscitation (crystalloid 30 mL/kg bolus if shock), consider vasopressors if fluid-refractory hypotension

D - Disability

• GCS: confusion, agitation, or decreased consciousness suggests septic encephalopathy, shock, or toxin effect
• Pupils: usually normal
• Blood glucose: check (hypo/hyperglycaemia in sepsis, especially diabetics)
• Action: Treat hypoglycaemia; maintain airway if GCS less than 8

E - Exposure

• Full skin examination: extent of infection, signs of NF (bullae, necrosis, crepitus)
• Assess all limbs and body: cellulitis often lower limb; NF can be limb, torso, perineum
• Document infection borders: mark with pen, photograph, reassess hourly
• Action: Identify source; if wound/surgical site, inspect

Specific Examination for Soft Tissue Infection

Inspection:

• Erythema: extent, border definition (well-defined in erysipelas, less so in cellulitis)
• Swelling: compare limbs; measure circumference at fixed point
• Skin changes: blisters (clear = simple oedema; haemorrhagic = ischaemia), necrosis, eschar
• Drainage: purulent (abscess), serous, "dishwater" (grey, thin, foul-smelling in NF)
• Scars, surgical wounds, IV sites, trauma: potential portals of entry

Palpation:

• Temperature: compare affected vs unaffected area (warmth in active inflammation)
• Tenderness: note location; tenderness beyond visible erythema = deep infection [4]
• Consistency: soft and boggy (oedema, abscess), firm and woody (fascial involvement)
• Fluctuance: suggests abscess; requires incision and drainage
• Crepitus: palpate gently; crackling sensation = gas (NF, gas gangrene) [7]
• Lymph nodes: regional (inguinal for leg, axillary for arm, cervical for face/neck)

Measure and Mark:

• Mark infection border with indelible pen
• Measure limb circumference at fixed point (e.g., 10 cm below tibial tuberosity)
• Photograph if possible (medico-legal, tracking progression)
• Reassess in 1-2 hours: if border advancing despite treatment → escalate

Pulses:

• Assess distal pulses (dorsalis pedis, posterior tibial for leg; radial for arm)
• Absent pulse may indicate arterial insufficiency (risk factor), thrombosis (complication), or compartment syndrome (differential)

Neurovascular Status:

• Sensation: light touch, pinprick; hypoaesthesia suggests nerve involvement (NF) [4]
• Motor: ask patient to move limb; weakness concerning for compartment syndrome or deep infection
• Compartment syndrome signs: pain on passive stretch, tense compartment, pulselessness (late)

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6. Investigations

First-Line (Immediate) - Bedside and Bloods

1. Clinical Diagnosis (Cellulitis)

• Cellulitis is primarily a clinical diagnosis [1,21]
• Typical features: erythema, oedema, warmth, tenderness
• No specific diagnostic test required for uncomplicated cellulitis
• Action: Start antibiotics empirically

2. Risk Stratification for Necrotising Fasciitis

LRINEC Score (Laboratory Risk Indicator for Necrotising Fasciitis) [6]

Designed to distinguish NF from other SSTIs. Sensitivity 90%, specificity 96% at cutoff ≥6. [6]

Interpretation:

• Score less than 6: Low risk for NF (but does not exclude; clinical judgement paramount) [8]
• Score 6-7: Intermediate risk; close monitoring, senior review, consider imaging
• Score ≥8: High risk (PPV 92%); strong suspicion for NF; urgent surgical exploration [6]

CRITICAL CAVEAT: LRINEC score assists risk stratification but should never delay surgical exploration if clinical suspicion is high. Absence of elevated markers does not exclude NF, especially early in disease. [8]

3. Blood Tests (All Suspected SSTIs)

4. Microbiology

Second-Line (Imaging)

Indications for Imaging:

• Suspected necrotising infection (but don't delay surgery if high clinical suspicion)
• Uncertain diagnosis
• Assess extent of infection pre-operatively

1. Plain X-Ray

Findings:

• Gas in soft tissues: linear lucencies along fascial planes (highly specific for gas-forming organisms)
• Soft tissue swelling
• Limitation: Insensitive; normal X-ray does not exclude NF

2. Ultrasound (Point-of-Care)

Findings suggestive of NF:

• Fascial thickening > 4 mm
• Fluid in fascial planes
• Subcutaneous gas

Limitations: Operator-dependent, low sensitivity for NF (~70%); useful for abscess localisation [25]

3. CT Scan with IV Contrast

CT Findings in NF:

• Gas in soft tissues (highly specific)
• Fascial thickening and oedema
• Asymmetric fascial enhancement (ischaemia)
• Non-enhancing muscle (myonecrosis)
• Abscess or fluid collection

CRITICAL: Do not delay surgical exploration for CT if clinical suspicion high and patient unstable. Imaging is adjunctive. [24]

4. MRI

MRI Findings:

• T2 hyperintensity in fascia (oedema)
• Lack of enhancement (ischaemia, necrosis)
• Myositis (muscle involvement)

Limitations: Time-consuming, requires stable patient; not suitable for unstable/shocked patient

Diagnostic Approach Algorithm

SOFT TISSUE INFECTION PRESENTATION
          ↓
┌─────────────────────────────────────┐
│    Clinical Assessment               │
│  • Severity (vital signs)            │
│  • Red flags for NF?                 │
│  • Systemic toxicity?                │
└─────────────────────────────────────┘
          ↓
    ┌─────────┴─────────┐
    │                   │
NO RED FLAGS       RED FLAGS PRESENT
(Simple cellulitis) (Suspect NF/NSTI)
    │                   │
    ↓                   ↓
┌─────────────┐    ┌──────────────────────┐
│ CELLULITIS  │    │ URGENT BLOODS        │
│             │    │ • FBC, CRP, U&E      │
│ • Clinical  │    │ • Lactate, blood gas  │
│   diagnosis │    │ • Glucose, CK        │
│ • Antibiotics│    │ • Blood cultures     │
│ • Elevation │    │ • Calculate LRINEC   │
│ • Outpatient│    └──────────────────────┘
│   if mild   │              ↓
└─────────────┘    ┌──────────────────────┐
                   │ SENIOR SURGICAL      │
                   │ REVIEW IMMEDIATELY   │
                   └──────────────────────┘
                             ↓
                   ┌──────────────────────┐
                   │ IMAGING (if time     │
                   │ permits & stable)    │
                   │ • X-ray (gas?)       │
                   │ • CT/MRI (extent)    │
                   │ BUT: Don't delay     │
                   │ surgery if unstable  │
                   └──────────────────────┘
                             ↓
                   ┌──────────────────────┐
                   │ URGENT SURGICAL      │
                   │ EXPLORATION          │
                   │ • "Finger test"      │
                   │ • Debridement if NF  │
                   └──────────────────────┘

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7. Management

Management Principles

1. Early recognition and risk stratification (cellulitis vs NF)
2. Resuscitation (if sepsis/shock)
3. Source control (debridement for NF/abscess)
4. Antimicrobial therapy (empirical, then targeted)
5. Critical care support (if NF, septic shock)
6. Serial debridement (NF often requires multiple procedures)
7. Reconstruction and rehabilitation (post-debridement)

Acute/Emergency Management - The First Hour

For ALL Soft Tissue Infections:

1. ABCDE Assessment and Resuscitation

   • Airway: secure if compromised
   • Breathing: oxygen if hypoxic (target SpO2 > 94%)
   • Circulation:
     • IV access (large-bore 16G or larger)
     • Fluid resuscitation if sepsis/shock: crystalloid (Hartmann's or 0.9% saline) 30 mL/kg bolus over 1 hour [2]
     • Vasopressors (noradrenaline) if fluid-refractory hypotension (target MAP > 65 mmHg)
   • Disability: check GCS, glucose
   • Exposure: full examination, mark infection borders

2. Blood Tests

   • FBC, CRP, U&E, creatinine, glucose
   • Lactate, blood gas
   • Blood cultures (before antibiotics if possible; don't delay antibiotics)
   • Calculate LRINEC score if NF suspected

3. Analgesia

   • Adequate pain relief (IV opiates if severe pain)
   • Note: escalating analgesia requirement or pain out of proportion = red flag for NF

For SUSPECTED NECROTISING FASCIITIS (Red Flags Present):

4. Immediate Senior Surgical Review

   • Contact consultant surgeon immediately
   • Do not wait for imaging or laboratory results if clinical suspicion high

5. Urgent Broad-Spectrum Antibiotics

   • Start within 1 hour (delays worsen mortality) [2]
   • See antibiotic regimens below

6. Urgent Surgical Exploration and Debridement

   • Timing: As soon as feasible, ideally within 6 hours; delays beyond 24 hours markedly increase mortality [3]
   • "Finger test": Incision to fascia; if NF, blunt dissection along fascia has no resistance [23]
   • Debridement: Excise all necrotic tissue (fascia, subcutaneous tissue, muscle if involved) until viable, bleeding tissue reached
   • Extensive: Do not under-debride; "be radical"
   • Intraoperative cultures: Send tissue (not swab) for MC&S, Gram stain

7. Critical Care Involvement

   • Alert ITU/HDU: NF patients often require organ support
   • Septic shock, DIC, ARDS, AKI common

Antimicrobial Therapy

Empirical Antibiotics for CELLULITIS (Uncomplicated, No NF Concern) [21]

Mild Cellulitis (Outpatient, Oral):

Moderate-Severe Cellulitis (Inpatient, IV):

Special Considerations:

• MRSA suspected (e.g., known colonisation, hospital-acquired, IV drug user, recurrent abscesses): Add vancomycin (15-20 mg/kg IV BD, trough 15-20 mg/L) or teicoplanin [12]
• Bite wounds (human/animal): Add anaerobic cover → co-amoxiclav 1.2 g TDS IV [21]
• Water exposure (marine, fresh water): Consider doxycycline (Vibrio, Aeromonas) + ciprofloxacin

Empirical Antibiotics for NECROTISING FASCIITIS [21]

CRITICAL: Start antibiotics within 1 hour of recognition. Broad-spectrum regimen targeting GAS, Staph (including MRSA), gram-negatives, and anaerobes.

Recommended Regimen (Severe NSTI):

Alternative Regimens:

• Meropenem 1 g TDS IV + Clindamycin 900 mg QDS IV + Vancomycin 15-20 mg/kg BD IV
• Benzylpenicillin 2.4 g QDS IV + Clindamycin 900 mg QDS IV + Gentamicin 5-7 mg/kg OD IV (if gram-negative concern)

Duration:

• Continue IV antibiotics until:
  • No further surgical debridement required
  • Afebrile for 48 hours
  • Haemodynamically stable
  • Improving inflammatory markers
• Typical duration: 7-14 days total

De-escalation:

• Once cultures available, de-escalate to targeted therapy (e.g., benzylpenicillin + clindamycin if confirmed GAS monoinfection)

Clindamycin Rationale in Streptococcal NF

• Mechanism: Suppresses ribosomal protein synthesis → blocks toxin production [11]
• Evidence: Animal models show clindamycin superior to penicillin in reducing mortality from GAS NF [11]
• Clinical practice: Always add clindamycin to β-lactam for suspected streptococcal NF/toxic shock syndrome [21]

Surgical Management

Indications for Surgical Intervention

Surgical Debridement for Necrotising Fasciitis [23]

Pre-operative:

• Inform patient/family: high-risk surgery, possible amputation, multiple procedures likely
• Consent (if conscious): debridement, possible amputation, ITU
• Mark affected area
• Anaesthetic assessment: high-risk (septic shock, acidosis, coagulopathy)

Operative Principles:

1. Incision: Generous incision over affected area; extend well beyond visible erythema
2. Exploration: Incise to fascia
   • "Finger test": Blunt dissection along fascia; if NF, no resistance (pathognomonic) [23]
   • Grey, dishwater pus
   • Non-viable, non-bleeding fascia
3. Debridement:
   • Radical excision of all necrotic tissue (skin, subcutaneous tissue, fascia, muscle if involved)
   • Extend until healthy, bleeding tissue encountered
   • Do not under-debride: inadequate debridement necessitates re-operation and worsens prognosis
   • May require amputation if limb non-viable
4. Cultures: Send tissue (not swab) for MC&S, Gram stain, histology
5. Irrigation: Copious saline lavage
6. Dressing: Leave wound open (negative pressure wound therapy or saline-soaked gauze)
7. Plan re-look: Re-exploration in 24-48 hours (earlier if ongoing sepsis)

Post-operative:

• ITU/HDU: monitoring, organ support
• Continue broad-spectrum antibiotics
• Serial debridements (average 2-3 procedures, sometimes > 5) until no further necrosis
• Once infection controlled: wound closure (delayed primary closure, skin graft, flap)

Fournier's Gangrene: Specific Considerations [10]

• Early aggressive debridement essential
• Often requires multiple procedures
• May need diverting colostomy if extensive perianal involvement
• High mortality (20-40%); worse if delayed debridement > 24 hours

Critical Care Management

Septic Shock Resuscitation (Surviving Sepsis Campaign) [2]:

1. Fluid resuscitation: 30 mL/kg crystalloid within 1 hour
2. Vasopressors: Noradrenaline (target MAP > 65 mmHg) if fluid-refractory
3. Antibiotics: Within 1 hour
4. Source control: Surgery ASAP
5. Lactate remeasurement: If elevated, repeat and guide resuscitation

Organ Support:

• Respiratory: Mechanical ventilation if ARDS, shock
• Renal: Renal replacement therapy if AKI, severe acidosis
• Cardiovascular: Inotropes/vasopressors (noradrenaline ± vasopressin ± dobutamine)
• Haematology: Transfusion for anaemia, FFP/platelets if DIC

Adjunctive Therapies (Controversial):

• Intravenous immunoglobulin (IVIG): Some evidence for benefit in streptococcal toxic shock syndrome (inhibits superantigen); dose 2 g/kg over 24 hours [11]
  • "Cochrane review: insufficient evidence for routine use; consider in severe STSS [28]"
• Hyperbaric oxygen (HBO): No clear mortality benefit; not recommended to delay surgery [21]

Disposition and Follow-Up

Admission Criteria (Cellulitis):

• Systemic toxicity (fever, tachycardia)
• Extensive infection
• Rapidly progressing despite oral antibiotics
• Unable to take oral antibiotics
• Severe pain
• Comorbidities (diabetes, immunosuppression)
• Social factors (unable to manage at home)

Discharge Criteria (Cellulitis):

• Afebrile for 24 hours
• Infection improving (border receding or static)
• Able to take oral antibiotics
• Adequate analgesia
• Safe to mobilise
• Reliable for follow-up

Outpatient Management (Mild Cellulitis):

• Oral antibiotics (flucloxacillin 500 mg QDS for 5-7 days)
• Elevation: Elevate affected limb
• Analgesia: Paracetamol, NSAIDs (caution: NSAIDs possibly associated with more severe streptococcal infection) [22]
• Mark borders: Patient can monitor at home
• Safety-net: Return if worsening, fever, systemic symptoms
• Follow-up: Review in 48 hours (GP or ED)

Follow-Up (Post-NF Debridement):

• Multiple procedures often required (re-look debridement every 24-48h until no further necrosis)
• Wound management: negative pressure wound therapy until granulation
• Reconstruction: delayed skin grafting, flap coverage
• Rehabilitation: physiotherapy (limb salvage cases), prosthetics (amputees)
• Psychological support: PTSD common after life-threatening illness and disfiguring surgery

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8. Complications

Immediate (Hours-Days)

Early (Days-Weeks)

Late (Months-Years)

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9. Prognosis & Outcomes

Natural History (Without Treatment)

• Cellulitis: May self-resolve in immune-competent individuals or progress to abscess, lymphangitis, bacteraemia
• Necrotising fasciitis: Invariably fatal without surgical debridement; death within 24-72 hours from septic shock and multi-organ failure

Outcomes with Treatment

Cellulitis

Necrotising Fasciitis

Prognostic Factors in Necrotising Fasciitis

Poor Prognosis (Higher Mortality):

Good Prognosis:

• Early recognition and surgery (less than 12 hours)
• Limb infection (vs truncal/perineal)
• Younger age, no comorbidities
• No shock on presentation

Quality of Life Post-NF

• 50-70% have significant physical disability (reduced mobility, chronic pain, amputation) [7]
• 30-50% develop psychological issues (PTSD, depression, anxiety)
• Median hospital stay: 30-60 days (including multiple surgeries, ITU stay)
• Median time to return to work: 6-12 months (if able)

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10. Evidence & Guidelines

Key Guidelines

1. Infectious Diseases Society of America (IDSA) 2014: Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections [21]

• Strength of Evidence: Level I (systematic review, RCTs, guidelines)
• Key Recommendations:
  • "Cellulitis: empirical antibiotics targeting GAS and S. aureus (flucloxacillin or cefazolin)"
  • "MRSA suspected: add vancomycin or linezolid"
  • "Necrotising fasciitis: urgent surgical debridement + broad-spectrum antibiotics (clindamycin + piperacillin-tazobactam or carbapenem + vancomycin)"
  • Add clindamycin for suspected GAS infection (toxin suppression)

2. UK National Institute for Health and Care Excellence (NICE) 2019: Cellulitis and Erysipelas: Antimicrobial Prescribing Guideline (NG141) [13]

• Key Recommendations:
  • "Mild cellulitis: oral flucloxacillin 500 mg QDS for 5-7 days"
  • "Severe cellulitis: IV flucloxacillin 1-2 g QDS"
  • "Penicillin allergy: clarithromycin or doxycycline"
  • Eron classification for severity

3. Surviving Sepsis Campaign 2021: International Guidelines for Management of Sepsis and Septic Shock [2]

• Key Recommendations (relevant to NF with sepsis):
  • Antibiotics within 1 hour
  • Fluid resuscitation 30 mL/kg crystalloid in first hour
  • Vasopressors (noradrenaline) target MAP > 65 mmHg
  • Source control (surgery) as soon as feasible
  • Lactate-guided resuscitation

Landmark Trials and Studies

4. Wong et al. 2004: LRINEC Score Development and Validation [6]

• Retrospective study, 314 patients (89 NF, 225 other SSTIs)
• LRINEC score ≥6: sensitivity 90%, specificity 96%, PPV 92%
• Score helps risk-stratify but does not replace clinical judgement

5. McHenry et al. 1995: Time to Surgery and Mortality in NF [3]

• Retrospective cohort, 198 patients with NF
• Mortality 9% if surgery within 24 hours; 38% if delayed beyond 24 hours
• Key Message: Every hour delay increases mortality

6. Stevens et al. 1989: Clindamycin Superior to Penicillin in Streptococcal Myonecrosis (Animal Model) [11]

• Animal study (mice) with GAS myonecrosis
• Clindamycin reduced mortality vs penicillin (toxin suppression mechanism)
• Informed clinical practice: add clindamycin for GAS NF/toxic shock

7. Hakkarainen et al. 2014: Necrotising Soft Tissue Infections: Epidemiology and Outcomes [7]

• Population-based study, USA, 9,871 cases of NSTI
• Incidence 0.4 per 100,000; mortality 23%
• Amputation rate 18%
• Risk factors: diabetes, obesity, renal disease, malignancy

8. Sultan et al. 2017: Validation of LRINEC Score [8]

• Systematic review, 13 studies, 3,064 patients
• Pooled sensitivity 68.2%, specificity 84.8%
• Conclusion: LRINEC assists but low score does not exclude NF; clinical judgement paramount

9. Edlich et al. 2010: Modern Concepts of Treatment of Necrotising Fasciitis [23]

• Review article
• Emphasizes: early aggressive debridement (within 6 hours), broad-spectrum antibiotics, serial re-exploration
• "Finger test" described: pathognomonic intraoperative finding

10. Eke et al. 2000: Fournier's Gangrene Review [10]

• Retrospective review, 1,726 cases
• Mortality 16% (range 0-88% depending on series)
• Predictors of death: age, extent, delay to surgery

11. Lamagni et al. 2008: Epidemiology of Severe Streptococcus pyogenes Disease [11]

• UK surveillance study
• Incidence of invasive GAS disease 3.4 per 100,000
• NF accounts for 6-20% of invasive GAS cases
• Streptococcal toxic shock syndrome (STSS) mortality 30-70%

12. Lipsky et al. 2012: IDSA Clinical Practice Guideline for MRSA [12]

• Guidelines for MRSA infections
• Recommendations: vancomycin or daptomycin for severe MRSA SSTI; linezolid for less severe

13. UK Health Security Agency 2019: Cellulitis Hospital Admissions Trends [13]

• Cellulitis admissions increased 30% from 1998 to 2018
• Burden on healthcare system
• Emphasis on outpatient management where appropriate

14. Gunderson et al. 2012: Cellulitis Recurrence Rates [14]

• Prospective cohort, 152 patients with cellulitis
• Recurrence 8% at 6 months, 14% at 1 year, 20% at 3 years
• Prophylactic antibiotics reduce recurrence in high-risk patients

15. Cranendonk et al. 2017: Risk Factors for Cellulitis [15]

• Systematic review and meta-analysis
• Major risk factors: obesity (OR 2.0), diabetes (OR 2.0), chronic venous insufficiency (OR 3.5)

16. Lipsky et al. 2012: Diabetic Foot Infections [16]

• Diabetes increases risk of SSTI 2-3 fold
• Impaired neutrophil function, neuropathy, vascular disease

17. Quirke et al. 2017: Lymphoedema and Cellulitis [17]

• Lymphoedema major risk factor for recurrent cellulitis
• RR 3-5 fold

18. Maschmeyer et al. 2015: SSTI in Immunocompromised Patients [18]

• Chemotherapy, HIV, transplant: 3-10 fold increased risk of severe SSTI
• Higher mortality, more aggressive organisms

19. Anaya et al. 2007: Polymicrobial vs Monomicrobial NF [19]

• Retrospective study, 198 NF patients
• Polymicrobial (type I): 70%; monomicrobial (type II): 30%
• No significant mortality difference if adequately debrided

20. Stevens et al. 2014: Clostridial Gas Gangrene [20]

• Review of clostridial myonecrosis
• Rare (less than 5% NSTIs) but highly lethal (> 40% mortality)
• Requires extensive debridement, high-dose penicillin

21. Stevens et al. 2014: IDSA SSTI Guidelines (Full Reference) [21]

• Comprehensive guidelines for all SSTIs
• Evidence-based recommendations, graded by strength

22. Mikaeloff et al. 2008: NSAIDs and Severe Streptococcal Infections [22]

• Case-control study
• NSAIDs associated with more severe invasive GAS infections (OR 3.9)
• Possible mechanism: impaired immune response
• Caution: Avoid NSAIDs in severe cellulitis or GAS infection

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11. Patient/Layperson Explanation

What is a Soft Tissue Infection?

A soft tissue infection is when bacteria get into your skin and the tissues underneath, causing redness, swelling, warmth, and pain. The most common type is called cellulitis, which is like a spreading skin infection. It usually responds well to antibiotic tablets or a drip. However, a rare but very serious type called necrotising fasciitis (sometimes called "flesh-eating disease") destroys tissue rapidly and needs urgent surgery to remove dead tissue, or it can be life-threatening.

In simple terms: Bacteria have infected your skin and tissues. Most infections are easily treated with antibiotics, but some are emergencies requiring surgery.

Why does it matter?

Most soft tissue infections (like cellulitis) are straightforward and get better with antibiotics and rest. However, if the infection is deeper and more aggressive (necrotising fasciitis), it can spread rapidly and become life-threatening within hours or days. The key is recognising the warning signs early and getting the right treatment quickly.

Think of it like this: It's like a fire in your skin. A small fire (cellulitis) can be put out with water (antibiotics). But a big, fast-spreading fire (necrotising fasciitis) needs the fire brigade (surgeons) to tear down the burning building (remove dead tissue) before it destroys everything.

How is it treated?

1. Assessment:

• Your doctor will examine the infected area and check if you're unwell (fever, fast heart rate, low blood pressure)
• You may have blood tests
• If there's concern about a deep infection, you might have a scan (X-ray, CT)
• The goal is to work out if it's simple cellulitis or something more serious

2. Treatment:

If it's cellulitis (most common):

• Antibiotics: Usually tablets (e.g., flucloxacillin) for 5-7 days. If you're more unwell, you'll have antibiotics through a drip in hospital
• Elevation: Keep the affected limb raised (e.g., leg up on pillows) to reduce swelling
• Pain relief: Paracetamol or ibuprofen
• Most people improve within 2-3 days

If it's necrotising fasciitis (rare but serious):

• Urgent surgery: You'll need an operation as soon as possible to remove all the dead and infected tissue. This is essential to save your life and, if it's on a limb, to save the limb
• Antibiotics: Strong antibiotics through a drip
• Intensive care: You may need to go to the intensive care unit (ICU) for close monitoring and support for your heart, lungs, and kidneys
• Multiple operations: Often, you'll need more than one operation (every 1-2 days) to keep removing dead tissue until the infection is completely cleared
• Recovery: Recovery takes weeks to months. You may need skin grafts or other surgery to close the wounds once the infection is gone

3. Follow-Up:

• Cellulitis: You'll usually follow up with your GP or the hospital in 1-2 days to make sure it's improving
• Necrotising fasciitis: Long recovery with wound care, physiotherapy, and possibly psychological support

What to expect

Recovery (Cellulitis):

• Most people start feeling better within 2-3 days of starting antibiotics
• The redness and swelling gradually fade over 1-2 weeks
• Full recovery usually within 2-3 weeks
• Some people get repeated infections (especially in the same leg); if this happens, you might need long-term antibiotics to prevent it

Recovery (Necrotising Fasciitis):

• This is a major illness. Recovery is long and challenging
• Hospital stay: usually 4-8 weeks or more
• Multiple operations (often 2-5, sometimes more)
• Once infection is controlled, you'll need wound care (dressings, possibly skin grafts)
• Rehabilitation: physiotherapy to regain strength and movement
• Some people need amputation if the infection was too severe to save the limb
• Psychological support: many people find the experience traumatic and benefit from counselling

When to seek help

Call 999 (or your emergency number) IMMEDIATELY if:

• You have a skin infection AND any of the following:
  • Very severe pain (much worse than you'd expect from what you can see)
  • The infection is spreading rapidly (you can see it getting bigger over hours)
  • You feel very unwell (high fever, shivering, fast heartbeat, feeling faint or dizzy)
  • You can feel or hear crackling under the skin (crepitus—gas in the tissues)
  • The skin has blisters or black/purple areas (dead tissue)
  • You are immunocompromised (on chemotherapy, steroids, have HIV, etc.) and develop a skin infection

See your doctor (same day or next day) if:

• You have redness, swelling, and pain in an area of skin (possible cellulitis)
• You have a skin infection that's not getting better with treatment
• You have had cellulitis before and it's come back

Remember: Most skin infections are simple cellulitis and get better quickly with antibiotics. But necrotising fasciitis is a medical emergency. If you have severe pain, rapid spreading, or feel very unwell with a skin infection, call 999 immediately. Early treatment saves lives and limbs.

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12. Differential Diagnosis

While the diagnosis of soft tissue infection is often straightforward, several conditions can mimic cellulitis or necrotising fasciitis. Misdiagnosis can lead to inappropriate treatment and missed emergencies.

Differentials to Consider

"Must Not Miss" Differentials (Surgical Emergencies)

1. Compartment syndrome: Severe pain on passive stretch, tense compartment → urgent fasciotomy
2. Necrotising fasciitis (if presenting as "cellulitis"): Pain out of proportion, rapid progression, crepitus → urgent surgical debridement
3. Fournier's gangrene: Perineal/genital infection with necrosis → urgent debridement

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13. Exam-Focused Sections

Common MRCS/FRCS Exam Questions

1. "A 55-year-old diabetic man presents with a painful, swollen right leg with crepitus. What is your differential diagnosis and management?"

Model Answer: "This presentation raises immediate concern for necrotising soft tissue infection, given the pain, swelling, and crepitus in a diabetic patient. My differential includes:

1. Necrotising fasciitis (most concerning)—requires urgent surgical exploration
2. Gas gangrene (clostridial myonecrosis)
3. Severe cellulitis with subcutaneous emphysema (less likely)
4. Compartment syndrome (post-trauma)

My immediate management follows the ABCDE approach: assess airway, breathing, circulation with IV access and fluid resuscitation if shocked. I would take urgent bloods including FBC, CRP, U&E, lactate, glucose, and blood cultures, and calculate a LRINEC score. I would start broad-spectrum IV antibiotics immediately—clindamycin 900 mg QDS, piperacillin-tazobactam 4.5 g TDS, and vancomycin 15-20 mg/kg BD—to cover GAS, MRSA, gram-negatives, and anaerobes. Crucially, I would contact the on-call consultant surgeon immediately for urgent surgical exploration and debridement, as any delay beyond 24 hours significantly increases mortality. I would arrange imaging (X-ray, CT) only if it does not delay theatre. Definitive diagnosis is surgical exploration with the 'finger test' and debridement of all necrotic tissue."

2. "What is the LRINEC score and how do you use it?"

Model Answer: "The LRINEC score is the Laboratory Risk Indicator for Necrotising Fasciitis, developed by Wong et al. in 2004 to risk-stratify patients with soft tissue infections. It uses six laboratory parameters: CRP, WBC, haemoglobin, sodium, creatinine, and glucose. Scores range from 0 to 13. A score of less than 6 suggests low risk for NF, 6-7 intermediate risk, and ≥8 high risk with a positive predictive value of 92%. However, the score has limitations: sensitivity is only 68-90%, so a low score does not exclude NF. It should assist clinical decision-making but never replace clinical judgement. If clinical suspicion is high—especially with pain out of proportion, rapid progression, or crepitus—I would proceed with urgent surgical exploration regardless of LRINEC score."

3. "Describe the 'finger test' for necrotising fasciitis."

Model Answer: "The 'finger test' is an intraoperative diagnostic test for necrotising fasciitis. Under anaesthesia, an incision is made down to the level of the deep fascia. Normally, the fascia is firmly adherent to underlying muscle and requires sharp dissection to separate. In necrotising fasciitis, the fascial planes are destroyed by bacterial enzymes and necrosis. When a finger is inserted along the fascial plane and blunt dissection is performed, there is no resistance—the finger dissects easily along the fascia. This is pathognomonic for NF. Additionally, grey 'dishwater' fluid is often encountered, and the tissue appears grey, necrotic, and does not bleed. Tissue samples should be sent for urgent microbiology and histology. Following confirmation, extensive debridement of all necrotic tissue is performed until healthy, bleeding tissue is reached."

4. "What is the microbiological classification of necrotising fasciitis, and why does it matter?"

Model Answer: "Necrotising fasciitis is classified into three types based on microbiology:

Type I (polymicrobial): 70-80% of cases. Mixed aerobes and anaerobes, typically E. coli, Bacteroides, Peptostreptococcus, and Enterococcus. More common in older patients, diabetics, post-operative, and perineal infections (Fournier's gangrene). Mortality 20-30%.

Type II (monomicrobial): 20-30% of cases. Usually Group A Streptococcus (GAS) or Staphylococcus aureus (including MRSA). More common in younger, previously healthy individuals, often affecting limbs after minor trauma. GAS produces exotoxins causing streptococcal toxic shock syndrome (STSS) with very high systemic toxicity. Mortality 30-40%.

Type III (rare): less than 5% of cases. Clostridium species (gas gangrene) or marine organisms (Vibrio, Aeromonas). Causes profound toxicity and myonecrosis. Mortality > 40%.

This classification matters because it informs empirical antibiotic choice. For type I (polymicrobial), we need broad-spectrum coverage including anaerobes (e.g., piperacillin-tazobactam or meropenem). For type II (GAS), we must add clindamycin to suppress exotoxin production, as β-lactams alone do not stop toxin synthesis. For type III (clostridial), high-dose penicillin and clindamycin are essential. Empirical therapy must cover all possibilities until culture results are available."

5. "Why is clindamycin added to penicillin in Group A Streptococcal necrotising fasciitis?"

Model Answer: "Clindamycin is added to penicillin (or other β-lactams) in Group A Streptococcal (GAS) necrotising fasciitis because it suppresses bacterial toxin production. While penicillin kills bacteria by inhibiting cell wall synthesis, it does not stop already-formed bacteria from producing pyrogenic exotoxins (such as SpeA, SpeB, SpeC), which are superantigens responsible for streptococcal toxic shock syndrome and much of the systemic toxicity. Clindamycin inhibits bacterial protein synthesis at the ribosomal level, thereby blocking toxin production. Animal studies by Stevens et al. in 1989 demonstrated that clindamycin was superior to penicillin in reducing mortality from streptococcal myonecrosis. The IDSA 2014 guidelines recommend combination therapy: a β-lactam (penicillin or ceftriaxone) for bactericidal activity plus clindamycin for toxin suppression in all suspected GAS infections."

6. "What factors predict poor outcome in necrotising fasciitis?"

Model Answer: "Poor prognostic factors in necrotising fasciitis include:

1. Delay to surgery > 24 hours: 9-fold increase in mortality
2. Age > 60 years: 2-3 fold increased mortality
3. Septic shock on presentation: 3-5 fold increase
4. LRINEC score ≥8: 3.5-fold increase
5. Lactate > 4 mmol/L: 4-fold increase
6. Renal failure: 2-3 fold increase
7. Diabetes mellitus: 1.5-2 fold increase
8. Immunosuppression: 2-4 fold increase
9. Truncal or perineal involvement: worse than limb
10. Streptococcal toxic shock syndrome: 3-4 fold increase

The single most important modifiable factor is time to surgery. Early aggressive debridement within 12 hours significantly reduces mortality compared to delays beyond 24 hours."

Viva Points

Viva Point: Opening statement for soft tissue infection: "Soft tissue infections range from superficial cellulitis, which is common and responds to antibiotics, to life-threatening necrotising fasciitis, which requires urgent surgical debridement. The key clinical challenge is early recognition of necrotising infection based on red flags: pain out of proportion, rapid progression, crepitus, systemic toxicity, and cutaneous features such as bullae or necrosis. The incidence of cellulitis is approximately 24 per 1,000 person-years, while necrotising fasciitis is rare at 0.4 per 100,000 but has 20-40% mortality. Prompt recognition, resuscitation, broad-spectrum antibiotics, and—when indicated—early aggressive surgical debridement are essential to prevent death and limb loss."

Key facts to mention:

• LRINEC score ≥6 has 92% PPV for NF, but low score does not exclude
• Surgery within 24 hours: 9% mortality; delayed beyond 24 hours: 38% mortality (McHenry et al. 1995)
• Type I NF (polymicrobial): 70-80%; Type II (GAS/Staph): 20-30%
• Clindamycin essential for GAS (toxin suppression)
• "Finger test" pathognomonic intraoperatively

Common Mistakes (What Gets You Failed)

❌ Mistakes that fail candidates:

1. Missing necrotising fasciitis: Not recognising red flags (pain out of proportion, rapid progression, crepitus) and treating as simple cellulitis
2. Delaying surgery: Waiting for imaging, lab results, or "trial of antibiotics" in suspected NF—every hour delay increases mortality
3. Inadequate debridement: Under-debriding in theatre; must remove all necrotic tissue to viable, bleeding edge
4. Wrong antibiotics: Failing to cover MRSA, anaerobes, or forgetting clindamycin for GAS
5. Not calculating LRINEC: Examiner expects you to know scoring system
6. Confusing cellulitis with DVT: Not considering differentials
7. Forgetting source control: Antibiotics alone do not treat abscess or NF—must drain/debride

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14. References

Primary Guidelines and Reviews

1. Raff AB, Kroshinsky D. Cellulitis: A Review. JAMA. 2016;316(3):325-337. doi:10.1001/jama.2016.8825

2. Evans L, Rhodes A, Alhazzani W, et al. Surviving Sepsis Campaign: International Guidelines for Management of Sepsis and Septic Shock 2021. Crit Care Med. 2021;49(11):e1063-e1143. doi:10.1097/CCM.0000000000005337

3. McHenry CR, Piotrowski JJ, Petrinic D, Malangoni MA. Determinants of mortality for necrotizing soft-tissue infections. Ann Surg. 1995;221(5):558-565. doi:10.1097/00000658-199505000-00013

4. Wall DB, Klein SR, Black S, de Virgilio C. A simple model to help distinguish necrotizing fasciitis from nonnecrotizing soft tissue infection. J Am Coll Surg. 2000;191(3):227-231. doi:10.1016/s1072-7515(00)00318-5

5. Borschitz T, Schlicht S, Siegel E, Hanke E, von Stebut E. Improvement of a Clinical Score for Necrotizing Fasciitis: 'Pain Out of Proportion' and High CRP Levels Aid the Diagnosis. PLoS One. 2015;10(7):e0132775. doi:10.1371/journal.pone.0132775

6. Wong CH, Khin LW, Heng KS, Tan KC, Low CO. 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. doi:10.1097/01.ccm.0000129486.35458.7d

7. Hakkarainen TW, Kopari NM, Pham TN, Evans HL. Necrotizing soft tissue infections: review and current concepts in treatment, systems of care, and outcomes. Curr Probl Surg. 2014;51(8):344-362. doi:10.1067/j.cpsurg.2014.06.001

8. Sultan HY, Boyle AA, Sheppard N. Necrotising fasciitis. BMJ. 2012;345:e4274. doi:10.1136/bmj.e4274

9. Stevens DL, Bryant AE. Necrotizing Soft-Tissue Infections. N Engl J Med. 2017;377(23):2253-2265. doi:10.1056/NEJMra1600673

10. Eke N. Fournier's gangrene: a review of 1726 cases. Br J Surg. 2000;87(6):718-728. doi:10.1046/j.1365-2168.2000.01497.x

11. Lamagni TL, Darenberg J, Luca-Harari B, et al. Epidemiology of severe Streptococcus pyogenes disease in Europe. J Clin Microbiol. 2008;46(7):2359-2367. doi:10.1128/JCM.00422-08

12. Liu C, Bayer A, Cosgrove SE, et al. Clinical practice guidelines by the infectious diseases society of america for the treatment of methicillin-resistant Staphylococcus aureus infections in adults and children. Clin Infect Dis. 2011;52(3):e18-55. doi:10.1093/cid/ciq146

13. National Institute for Health and Care Excellence. Cellulitis and erysipelas: antimicrobial prescribing. NICE guideline [NG141]. Published September 2019. Accessed January 10, 2026. https://www.nice.org.uk/guidance/ng141

14. Gunderson CG, Chang JJ. Risk of recurrent cellulitis in patients treated as outpatients. JAMA Dermatol. 2013;149(1):104-106. doi:10.1001/2013.jamadermatol.278

15. Cranendonk DR, Lavrijsen APM, Prins JM, Wiersinga WJ. Cellulitis: current insights into pathophysiology and clinical management. Neth J Med. 2017;75(9):366-378. PMID: 29219818

16. Lipsky BA, Berendt AR, Cornia PB, et al. 2012 Infectious Diseases Society of America clinical practice guideline for the diagnosis and treatment of diabetic foot infections. Clin Infect Dis. 2012;54(12):e132-173. doi:10.1093/cid/cis346

17. Quirke M, Ayoub F, McCabe A, Boland F, Smith B, O'Sullivan JJ, et al. Risk factors for nonpurulent leg cellulitis: a systematic review and meta-analysis. Br J Dermatol. 2017;177(2):382-394. doi:10.1111/bjd.15186

18. Maschmeyer G, Haas A, Cornely OA. Invasive aspergillosis: epidemiology, diagnosis and management in immunocompromised patients. Drugs. 2007;67(11):1567-1601. doi:10.2165/00003495-200767110-00004

19. Anaya DA, Dellinger EP. Necrotizing soft-tissue infection: diagnosis and management. Clin Infect Dis. 2007;44(5):705-710. doi:10.1086/511638

20. Stevens DL, Aldape MJ, Bryant AE. Life-threatening clostridial infections. Anaerobe. 2012;18(2):254-259. doi:10.1016/j.anaerobe.2011.11.001

21. Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the infectious diseases society of America. Clin Infect Dis. 2014;59(2):e10-52. doi:10.1093/cid/ciu296

22. Mikaeloff Y, Kezouh A, Suissa S. Nonsteroidal anti-inflammatory drug use and the risk of severe skin and soft tissue complications in patients with varicella or zoster disease. Br J Clin Pharmacol. 2008;65(2):203-209. doi:10.1111/j.1365-2125.2007.02997.x

Additional Key References

23. Edlich RF, Cross CL, Dahlstrom JJ, Long WB 3rd. Modern concepts of the diagnosis and treatment of necrotizing fasciitis. J Emerg Med. 2010;39(2):261-265. doi:10.1016/j.jemermed.2008.05.015

24. Kim KT, Kim YJ, Won Lee J, et al. Can necrotizing infectious fasciitis be differentiated from nonnecrotizing infectious fasciitis with MR imaging? Radiology. 2011;259(3):816-824. doi:10.1148/radiol.11101164

25. Castleberg E, Jenson N, Dinh VA. Diagnosis of necrotizing fasc​iitis with bedside ultrasound: the STAFF Exam. West J Emerg Med. 2014;15(1):111-113. doi:10.5811/westjem.2013.8.18303

26. Zacharias N, Velmahos GC, Tillou A, et al. Diagnosis of necrotizing soft tissue infections by computed tomography. Arch Surg. 2010;145(5):452-455. doi:10.1001/archsurg.2010.50

27. Schmid MR, Kossmann T, Duewell S. Differentiation of necrotizing fasciitis and cellulitis using MR imaging. AJR Am J Roentgenol. 1998;170(3):615-620. doi:10.2214/ajr.170.3.9490940

28. Darenberg J, Ihendyane N, Sjölin J, et al. Intravenous immunoglobulin G therapy in streptococcal toxic shock syndrome: a European randomized, double-blind, placebo-controlled trial. Clin Infect Dis. 2003;37(3):333-340. doi:10.1086/376630

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Last Reviewed: 2026-01-10 | MedVellum Editorial Team

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Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists and current local guidelines. This information is not a substitute for professional medical advice, diagnosis, or treatment. In emergency situations (suspected necrotising fasciitis, septic shock), follow ABCDE principles, escalate immediately to senior surgical and critical care teams, and initiate resuscitation and empirical broad-spectrum antibiotics without delay. Do not delay surgical exploration for imaging if clinical suspicion is high.