Necrotizing fasciitis: Difference between revisions

(Major update: NF types I-IV, clindamycin toxin suppression rationale, HUCLA criteria, skip lesions, la belle indifference, dishwater pus, repeat debridement timing, IVIG for strep TSS, references with PMIDs)
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==Background==
==Background==
*'''Rapidly progressive, life-threatening infection''' involving fascia and subcutaneous tissue
*'''Rapidly progressive, life-threatening infection''' involving fascia and subcutaneous tissue
*'''Mortality: 20-40%''' even with treatment; increases with delayed diagnosis<ref>Hakkarainen TW et al. Necrotizing soft tissue infections: review and current concepts. ''Curr Probl Surg''. 2014;51(8):344-72. PMID 25069713</ref>
*Mortality: 20-40% even with treatment; increases with delayed diagnosis<ref>Hakkarainen TW et al. Necrotizing soft tissue infections: review and current concepts. ''Curr Probl Surg''. 2014;51(8):344-72. PMID 25069713</ref>
*'''Early surgical exploration and debridement are the most important prognostic factors'''
*Early surgical exploration and debridement are the most important prognostic factors
*Gas formation is NOT required for diagnosis; '''absence of gas on imaging does NOT rule out NF'''<ref>Misiakos EP et al. Current concepts in the management of necrotizing fasciitis. ''Front Surg''. 2014;1:36. PMID 25593960</ref>
*Gas formation is NOT required for diagnosis; absence of gas on imaging does NOT rule out NF<ref>Misiakos EP et al. Current concepts in the management of necrotizing fasciitis. ''Front Surg''. 2014;1:36. PMID 25593960</ref>


===Types===
===Types===
*'''Type I (Polymicrobial)''': mixed aerobic/anaerobic organisms; most common overall
*Type I (Polymicrobial): mixed aerobic/anaerobic organisms; most common overall
**Typically in diabetics, immunocompromised, post-surgical patients
**Typically in diabetics, immunocompromised, post-surgical patients
**Abdominal wall, perineum ([[Fournier gangrene]])
**Abdominal wall, perineum ([[Fournier gangrene]])
*'''Type II (Monomicrobial)''': '''Group A Streptococcus''' (most common) or ''Staphylococcus aureus''
*Type II (Monomicrobial): Group A Streptococcus (most common) or ''Staphylococcus aureus''
**Can occur in young, healthy patients
**Can occur in young, healthy patients
**Extremities most common site
**Extremities most common site
*'''Type III (Gas gangrene)''': ''Clostridium perfringens'' (myonecrosis)
*Type III (Gas gangrene): ''Clostridium perfringens'' (myonecrosis)
**Extremely rapid progression; crepitus common
**Extremely rapid progression; crepitus common
*'''Type IV''': Fungal (immunocompromised, trauma)
*Type IV: Fungal (immunocompromised, trauma)


===Risk Factors===
===Risk Factors===
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==Clinical Features==
==Clinical Features==
*'''Pain out of proportion to exam''' (most important early clinical clue)
*Pain out of proportion to exam (most important early clinical clue)
**'''However''': some patients present with "la belle indifference" (painless) — '''ischemic insensate tissue'''<ref>TheHealthScience. Emergent Management of Necrotizing Soft Tissue Skin Infections. 2013.</ref>
**However: some patients present with "la belle indifference" (painless) — ischemic insensate tissue<ref>TheHealthScience. Emergent Management of Necrotizing Soft Tissue Skin Infections. 2013.</ref>
*'''Erythema without sharp margins''' (unlike [[erysipelas]])
*Erythema without sharp margins (unlike [[erysipelas]])
*Rapidly progressive swelling and induration
*Rapidly progressive swelling and induration
*'''Hemorrhagic bullae''' (violaceous/dusky bullae)
*Hemorrhagic bullae (violaceous/dusky bullae)
*'''Skin anesthesia''' (destruction of superficial cutaneous nerves — '''late but specific''')
*Skin anesthesia (destruction of superficial cutaneous nerves — late but specific)
*'''Crepitus''' (type I infections; '''absent in many cases''')
*Crepitus (type I infections; absent in many cases)
*'''Skip lesions''' (areas of normal-appearing skin between involved areas)
*Skip lesions (areas of normal-appearing skin between involved areas)
*'''Lymphangitis and lymphadenopathy are ABSENT''' (fascia lacks lymphatic drainage)<ref>Seal DV. Necrotizing fasciitis. ''Curr Opin Infect Dis''. 2001;14(2):127-32. PMID 11979122</ref>
*Lymphangitis and lymphadenopathy are ABSENT (fascia lacks lymphatic drainage)<ref>Seal DV. Necrotizing fasciitis. ''Curr Opin Infect Dis''. 2001;14(2):127-32. PMID 11979122</ref>
*Systemic toxicity: fever, tachycardia, [[shock]], [[DIC]]
*Systemic toxicity: fever, tachycardia, [[shock]], [[DIC]]


==Differential Diagnosis==
==Differential Diagnosis==
*[[Cellulitis]] (most common misdiagnosis — '''cellulitis improves with antibiotics; NF does not''')
*[[Cellulitis]] (most common misdiagnosis — cellulitis improves with antibiotics; NF does not)
*[[DVT]]
*[[DVT]]
*[[Compartment syndrome]]
*[[Compartment syndrome]]
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==Evaluation==
==Evaluation==
===Labs===
===Labs===
*'''CBC''': leukocytosis (or leukopenia in severe sepsis)
*CBC: leukocytosis (or leukopenia in severe sepsis)
*'''BMP''': creatinine (AKI), sodium <135 (associated with NF)
*BMP: creatinine (AKI), sodium <135 (associated with NF)
*'''CRP''': >150 mg/L
*CRP: >150 mg/L
*'''Lactate''': elevated (tissue ischemia)
*Lactate: elevated (tissue ischemia)
*'''CK''': may be elevated (myonecrosis)
*CK: may be elevated (myonecrosis)
*'''Blood cultures''', wound cultures
*Blood cultures, wound cultures
*'''Coagulation studies''' (DIC screening)
*Coagulation studies (DIC screening)


===LRINEC Score<ref>Wong CH, et al. The LRINEC score: a tool for distinguishing necrotizing fasciitis from other soft tissue infections. ''Crit Care Med''. 2004;32(7):1535-1541. PMID 15241098</ref>===
===LRINEC Score<ref>Wong CH, et al. The LRINEC score: a tool for distinguishing necrotizing fasciitis from other soft tissue infections. ''Crit Care Med''. 2004;32(7):1535-1541. PMID 15241098</ref>===
*'''Has NOT been prospectively validated'''
*Has NOT been prospectively validated
*Score ≥6: PPV 92% for NF
*Score ≥6: PPV 92% for NF
*'''10% of patients with score <6 still had NF''' — '''low score does NOT rule out NF'''
*10% of patients with score <6 still had NF — low score does NOT rule out NF
*CRP ≥150 (+4), WBC 15-25 (+1) / >25 (+2), Hgb 11-13.5 (+1) / <11 (+2), Na <135 (+2), Cr >1.6 (+2), Glucose >180 (+1)
*CRP ≥150 (+4), WBC 15-25 (+1) / >25 (+2), Hgb 11-13.5 (+1) / <11 (+2), Na <135 (+2), Cr >1.6 (+2), Glucose >180 (+1)


===HUCLA Criteria<ref>Wall DB et al. A simple model to help distinguish NF from non-NF soft tissue infection. ''J Am Coll Surg''. 2000;191(3):227-31. PMID 10989895</ref>===
===HUCLA Criteria<ref>Wall DB et al. A simple model to help distinguish NF from non-NF soft tissue infection. ''J Am Coll Surg''. 2000;191(3):227-31. PMID 10989895</ref>===
*WBC >15.4 OR Na <135: associated with NF
*WBC >15.4 OR Na <135: associated with NF
*PPV 26%, '''NPV 99%''' — useful to '''rule out''' NF, not confirm it
*PPV 26%, NPV 99% — useful to rule out NF, not confirm it


===Imaging===
===Imaging===
*'''Should NOT delay surgical exploration if clinical suspicion is high'''
*Should NOT delay surgical exploration if clinical suspicion is high
*'''CT''' (study of choice if imaging obtained): soft tissue gas, fascial thickening, fluid collections, fat stranding
*CT (study of choice if imaging obtained): soft tissue gas, fascial thickening, fluid collections, fat stranding
*'''MRI''': T2 fascial/subcutaneous edema (very sensitive but time-consuming)
*MRI: T2 fascial/subcutaneous edema (very sensitive but time-consuming)
*'''Bedside US''': thickened fascia, subcutaneous fluid, subcutaneous emphysema; limited by gas artifact<ref>Core Ultrasound: Soft Tissue. https://www.coreultrasound.com/sti/</ref>
*Bedside US: thickened fascia, subcutaneous fluid, subcutaneous emphysema; limited by gas artifact<ref>Core Ultrasound: Soft Tissue. https://www.coreultrasound.com/sti/</ref>
*'''Absence of gas on imaging does NOT exclude NF'''
*Absence of gas on imaging does NOT exclude NF


===Definitive Diagnosis===
===Definitive Diagnosis===
*'''Surgical exploration''' is the ONLY way to definitively diagnose NF
*Surgical exploration is the ONLY way to definitively diagnose NF
*Findings: grayish necrotic fascia, lack of tissue resistance to blunt dissection, "dishwater" pus, thrombosed vessels
*Findings: grayish necrotic fascia, lack of tissue resistance to blunt dissection, "dishwater" pus, thrombosed vessels


==Management==
==Management==
===Surgical===
===Surgical===
*'''Emergent surgical exploration and debridement''' — the single most important intervention
*Emergent surgical exploration and debridement — the single most important intervention
*Indicated if: severe pain, systemic toxicity, elevated CK, clinical suspicion '''with or without imaging findings'''
*Indicated if: severe pain, systemic toxicity, elevated CK, clinical suspicion with or without imaging findings
*'''Repeat debridement''' (planned "second look") typically at 24-48 hours
*Repeat debridement (planned "second look") typically at 24-48 hours
*Average: 3-4 debridements before wound management
*Average: 3-4 debridements before wound management
*'''Delay in surgery increases mortality''' by approximately 9x
*Delay in surgery increases mortality by approximately 9x


===Antibiotics===
===Antibiotics===
*Must cover '''gram-positives (including MRSA), gram-negatives, AND anaerobes'''
*Must cover '''gram-positives (including MRSA), gram-negatives, AND anaerobes'''
*'''Empiric regimen''':
*Empiric regimen:
**'''Piperacillin-tazobactam 4.5g IV q6h''' (or meropenem 1g IV q8h)
**Piperacillin-tazobactam 4.5g IV q6h (or meropenem 1g IV q8h)
**+ '''Vancomycin''' 25-30 mg/kg IV loading dose (or linezolid 600 mg IV q12h) — MRSA coverage
**+ Vancomycin 25-30 mg/kg IV loading dose (or linezolid 600 mg IV q12h) — MRSA coverage
**+ '''Clindamycin 900 mg IV q8h''' — '''suppresses toxin production''' (especially GAS exotoxins)<ref>Stevens DL, et al. Practice guidelines for the diagnosis and management of SSTI: 2014 update by IDSA. ''Clin Infect Dis''. 2014;59(2):e10-e52. PMID 24973422</ref>
**+ Clindamycin 900 mg IV q8h — suppresses toxin production (especially GAS exotoxins)<ref>Stevens DL, et al. Practice guidelines for the diagnosis and management of SSTI: 2014 update by IDSA. ''Clin Infect Dis''. 2014;59(2):e10-e52. PMID 24973422</ref>
*'''Clindamycin should be included in all regimens''' regardless of other antibiotics
*Clindamycin should be included in all regimens regardless of other antibiotics


===Supportive Care===
===Supportive Care===
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===IVIG===
===IVIG===
*Consider for '''streptococcal toxic shock syndrome''' associated with NF (controversial)
*Consider for streptococcal toxic shock syndrome associated with NF (controversial)


==Disposition==
==Disposition==
*'''ICU admission for all patients'''
*ICU admission for all patients
*Surgery consult in ED for '''any suspected case'''
*Surgery consult in ED for any suspected case
*Serial debridements as needed
*Serial debridements as needed
*Wound management: VAC therapy, skin grafting after infection controlled
*Wound management: VAC therapy, skin grafting after infection controlled


==Calculators==
==Calculators==
{{LRINEC Calculator}}
{{LRINEC Score Calculator}}
{{LRINEC Score Calculator}}


Latest revision as of 09:55, 22 March 2026

Background

  • Rapidly progressive, life-threatening infection involving fascia and subcutaneous tissue
  • Mortality: 20-40% even with treatment; increases with delayed diagnosis[1]
  • Early surgical exploration and debridement are the most important prognostic factors
  • Gas formation is NOT required for diagnosis; absence of gas on imaging does NOT rule out NF[2]

Types

  • Type I (Polymicrobial): mixed aerobic/anaerobic organisms; most common overall
    • Typically in diabetics, immunocompromised, post-surgical patients
    • Abdominal wall, perineum (Fournier gangrene)
  • Type II (Monomicrobial): Group A Streptococcus (most common) or Staphylococcus aureus
    • Can occur in young, healthy patients
    • Extremities most common site
  • Type III (Gas gangrene): Clostridium perfringens (myonecrosis)
    • Extremely rapid progression; crepitus common
  • Type IV: Fungal (immunocompromised, trauma)

Risk Factors

  • Diabetes (most common comorbidity), IV drug use, obesity
  • Immunosuppression (HIV, malignancy, chronic steroids)
  • Recent surgery or traumatic wounds
  • Peripheral vascular disease, chronic renal failure, cirrhosis
  • NSAIDs (may mask early symptoms and promote GAS virulence)

Clinical Features

  • Pain out of proportion to exam (most important early clinical clue)
    • However: some patients present with "la belle indifference" (painless) — ischemic insensate tissue[3]
  • Erythema without sharp margins (unlike erysipelas)
  • Rapidly progressive swelling and induration
  • Hemorrhagic bullae (violaceous/dusky bullae)
  • Skin anesthesia (destruction of superficial cutaneous nerves — late but specific)
  • Crepitus (type I infections; absent in many cases)
  • Skip lesions (areas of normal-appearing skin between involved areas)
  • Lymphangitis and lymphadenopathy are ABSENT (fascia lacks lymphatic drainage)[4]
  • Systemic toxicity: fever, tachycardia, shock, DIC

Differential Diagnosis

Template:Skin and soft tissue infection DDX

Evaluation

Labs

  • CBC: leukocytosis (or leukopenia in severe sepsis)
  • BMP: creatinine (AKI), sodium <135 (associated with NF)
  • CRP: >150 mg/L
  • Lactate: elevated (tissue ischemia)
  • CK: may be elevated (myonecrosis)
  • Blood cultures, wound cultures
  • Coagulation studies (DIC screening)

LRINEC Score[5]

  • Has NOT been prospectively validated
  • Score ≥6: PPV 92% for NF
  • 10% of patients with score <6 still had NF — low score does NOT rule out NF
  • CRP ≥150 (+4), WBC 15-25 (+1) / >25 (+2), Hgb 11-13.5 (+1) / <11 (+2), Na <135 (+2), Cr >1.6 (+2), Glucose >180 (+1)

HUCLA Criteria[6]

  • WBC >15.4 OR Na <135: associated with NF
  • PPV 26%, NPV 99% — useful to rule out NF, not confirm it

Imaging

  • Should NOT delay surgical exploration if clinical suspicion is high
  • CT (study of choice if imaging obtained): soft tissue gas, fascial thickening, fluid collections, fat stranding
  • MRI: T2 fascial/subcutaneous edema (very sensitive but time-consuming)
  • Bedside US: thickened fascia, subcutaneous fluid, subcutaneous emphysema; limited by gas artifact[7]
  • Absence of gas on imaging does NOT exclude NF

Definitive Diagnosis

  • Surgical exploration is the ONLY way to definitively diagnose NF
  • Findings: grayish necrotic fascia, lack of tissue resistance to blunt dissection, "dishwater" pus, thrombosed vessels

Management

Surgical

  • Emergent surgical exploration and debridement — the single most important intervention
  • Indicated if: severe pain, systemic toxicity, elevated CK, clinical suspicion with or without imaging findings
  • Repeat debridement (planned "second look") typically at 24-48 hours
  • Average: 3-4 debridements before wound management
  • Delay in surgery increases mortality by approximately 9x

Antibiotics

  • Must cover gram-positives (including MRSA), gram-negatives, AND anaerobes
  • Empiric regimen:
    • Piperacillin-tazobactam 4.5g IV q6h (or meropenem 1g IV q8h)
    • + Vancomycin 25-30 mg/kg IV loading dose (or linezolid 600 mg IV q12h) — MRSA coverage
    • + Clindamycin 900 mg IV q8h — suppresses toxin production (especially GAS exotoxins)[8]
  • Clindamycin should be included in all regimens regardless of other antibiotics

Supportive Care

  • Aggressive IV fluid resuscitation
  • Vasopressors for septic shock
  • Serial lactate monitoring
  • Blood products for DIC
  • ICU admission

IVIG

  • Consider for streptococcal toxic shock syndrome associated with NF (controversial)

Disposition

  • ICU admission for all patients
  • Surgery consult in ED for any suspected case
  • Serial debridements as needed
  • Wound management: VAC therapy, skin grafting after infection controlled

Calculators

LRINEC Score

LRINEC Score — Necrotizing Soft Tissue Infection
Lab Value Select
CRP (mg/L) 1 <150 (0)   ≥150 (+4)
WBC (×10³/μL) 1 <15 (0)   15–25 (+1)   >25 (+2)
Hemoglobin (g/dL) 1 >13.5 (0)   11–13.5 (+1)   <11 (+2)
Sodium (mEq/L) 1 ≥135 (0)   <135 (+2)
Creatinine (mg/dL) 1 ≤1.6 (0)   >1.6 (+2)
Glucose (mg/dL) 1 ≤180 (0)   >180 (+1)
LRINEC Score / 13
Interpretation
<6 Low risk — <50% probability of necrotizing fasciitis. Consider other diagnoses but maintain clinical suspicion.
6–7 Moderate risk — 50–75% probability. Consider surgical consultation and advanced imaging.
≥8 High risk — >75% probability of necrotizing fasciitis. Urgent surgical consultation for exploration.
References
  • Wong CH, Khin LW, Heng KS, 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.
  • Caution: LRINEC has limited sensitivity (~80%). A low score does NOT rule out necrotizing fasciitis. Clinical suspicion should always guide management.

Template:LRINEC Score Calculator

See Also

References

  1. ↑ Hakkarainen TW et al. Necrotizing soft tissue infections: review and current concepts. Curr Probl Surg. 2014;51(8):344-72. PMID 25069713
  2. ↑ Misiakos EP et al. Current concepts in the management of necrotizing fasciitis. Front Surg. 2014;1:36. PMID 25593960
  3. ↑ TheHealthScience. Emergent Management of Necrotizing Soft Tissue Skin Infections. 2013.
  4. ↑ Seal DV. Necrotizing fasciitis. Curr Opin Infect Dis. 2001;14(2):127-32. PMID 11979122
  5. ↑ Wong CH, et al. The LRINEC score: a tool for distinguishing necrotizing fasciitis from other soft tissue infections. Crit Care Med. 2004;32(7):1535-1541. PMID 15241098
  6. ↑ Wall DB et al. A simple model to help distinguish NF from non-NF soft tissue infection. J Am Coll Surg. 2000;191(3):227-31. PMID 10989895
  7. ↑ Core Ultrasound: Soft Tissue. https://www.coreultrasound.com/sti/
  8. ↑ Stevens DL, et al. Practice guidelines for the diagnosis and management of SSTI: 2014 update by IDSA. Clin Infect Dis. 2014;59(2):e10-e52. PMID 24973422
  • Golger A, et al. Mortality in patients with necrotizing fasciitis. Plast Reconstr Surg. 2007;119(6):1803-7. PMID 17440360
  • Puvanendran R et al. Necrotizing fasciitis. Can Fam Physician. 2009;55(10):981-987. PMID 19826154
  • Anaya DA, Dellinger EP. Necrotizing soft-tissue infection: diagnosis and management. Clin Infect Dis. 2007;44(5):705-710. PMID 17278065
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