Necrotizing fasciitis


  • A rapidly progressive infection primarily involving the fascia and subcutaneous tissue
  • Formerly a rare diagnosis, frequency has risen due to an increase in immunocompromised patients with significant risk factors[1]
  • Gas-formation is NOT a requirement for diagnosis, and radiographical lack of the classically taught gas formation should NEVER rule out necrotizing infection[2]
  • Most severe form of soft tissue infection and potentially limb and life threatening
  • Early recognition and aggressive debridement are major prognostic determinants and delay increases mortality[3]


Risk Factors

  • DM
  • Drug use
  • Obesity
  • Immunosuppression
  • Recent surgery
  • Traumatic wounds

Clinical Features

Nectrotizing fasciitis
  • Skin exam
    • Erythema (without sharp margins)
    • Exquisitely tender (pain out of proportion to exam)
      • Caveat - some patients present with "la belle indifference"
      • May be a result of ischemic, insensate tissue[4]
    • Skip lesions
    • Hemorrhagic bullae (violaceous bullae)
      • May be preceded by skin anesthesia (destruction of superficial nerves)
    • Crepitus (in type I infections)
    • Lymphangitis and lymphadenopathy are absent in necrotizing fasciitis alone[5][6]
      • Lymphangitis is seen in cellulitis
      • Fascia has no lymph drainage
  • Swelling/edema may produce compartment syndrome
  • Constitutional or toxic shock-like syndrome[7]

Differential Diagnosis

Skin and Soft Tissue Infection


Necrotizing rashes


CT of necrotizing fasciitis


  • CBC
  • Chem
  • CK
  • Lactate


  • Surgical exploration is the ONLY way to definitively establish the diagnosis of necrotizing infection
  • Imaging
    • Should not delay surgical exploration
    • CT is study of choice - soft tissue gas, edema and fluid collections, fascial thickening with fat stranding
    • US may show thickened fascial planes, fluid between fascial planes, irregularity of the fascia, subcutaneous emphysema. The study may be limited by soft tissue gas. Video lecture[8].
    • MRI - T2 subcutaneous, intramuscular, and fascial edema
  • Absence of gas on imaging does not exclude diagnosis, as gas may be occult and/or certain organisms do not classically produce gas (i.e. Group A Strep)

Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) Score[9]

Has not been prospectively validated, index of suspicion is key and 10% of the patients with a score < 6 had Necrotizing Fasciitis. A score > 6 has PPV of 92% and NPV of 96% for necrotizing fasciitis.

  1. CRP (mg/L) ≥150: 4 points
  2. WBC count (×103/mm3)
    • <15: 0 points
    • 15–25: 1 point
    • >25: 2 points
  3. Hemoglobin (g/dL)
    • >13.5: 0 points
    • 11–13.5: 1 point
    • <11: 2 points
  4. Sodium (mmol/L) <135: 2 points
  5. Creatinine (umol/L) >141: 2 points
  6. Glucose >180 mg/dL (10 mmol/L): 1 point

Grouping by Scores

  • Low Risk: score 5 (10% of pts with score < 6 still had nec fasc)
  • Moderate Risk: score 6– 7
  • High Risk: score >8

Proposed algorithm

HUCLA NF vs Non-NF Criteria:[10]

  • Retrospective study discovered:
    • WBC count >15.4(x103/mm3) OR Na <135(mmol/L)
    • Associated with NF and combo of both increased likelihood of NF
    • PPV 26%/NPV 99%
  • Useful tool to rule out NF, not a good tool for confirming presence of NF
    • Helps distinguish NF from non-NF infection, when classic 'hard' signs of NF are absent however clinical judgment should still be used in patient with high suspicion of the disease



  • Admit to ICU

See Also


  1. Hakkarainen TW et al. Necrotizing soft tissue infections: review and current concepts in treatment, systems of care, and outcomes. Curr Probl Surg. 2014 Aug. 51 (8):344-72.
  2. Misiakos EP et al. Current concepts in the management of necrotizing fasciitis. Front Surg. 2014. 1:36.
  3. Wong CH, Khin LW, Heng KS, Tan KC, Low CO (2004). "The LRINEC Laboratory Rother soft tissue infections". Critical Care Medicine 32 (7): 1535–1541. doi:10.1097/01.CCM.0000129486.35458.7D. PMID 15241098
  4. TheHealthScience. Emergent Management of Necrotizing Soft Tissue Skin Infections. Nov 22, 2013.
  5. Seal DV. Necrotizing fasciitis. Curr Opin Infect Dis. 2001;14(2):127–32.
  6. Golger A, Ching S, Goldsmith CH, Pennie RA, Bain JR. Mortality in patients with necrotizing fasciitis. Plast Reconstr Surg. 2007;119(6):1803–7.
  7. Puvanendran R et al. Necrotizing fasciitis. Can Fam Physician. 2009 Oct; 55(10): 981–987.
  8. Soft Tissue Ultrasound with Jacob Avila on Core Ultrasound.
  9. Wong C. "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):1535-41.
  10. Wall DB et al. A simple model to help distinguish necrotizing fasciitis from nonnecrotizing soft tissue infection. J Am Coll Surg. 2000 Sep;191(3):227-31.
  11. 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 [published correction appears in Clin Infect Dis. 2015 May 1;60(9):1448. Dosage error in article text]. Clin Infect Dis. 2014;59(2):e10-e52. doi:10.1093/cid/ciu444