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    Necrotizing Fasciitis – Diagnosis


    Last Updated Nov 01, 2022
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    • Necrotizing fasciitis is a rare but life/limb threatening disease and is a true surgical emergency.
    • There are about 100 cases annually in Canada (1/350,000).
    • There are 3 types:
      • Type I: Polymicrobial: Typical risk factors include diabetes, peripheral vascular disease (PVD), and advanced age. Can occur in urogenital region (Fournier’s gangrene).
      • Type II: Group A streptococcal necrotizing fasciitis (“flesh-eating disease”). Few or no risk factors.
      • Type III: Clostridial myonecrosis (gas gangrene). This skeletal muscle infection may be associated with recent surgery or trauma.

    Diagnostic Process

    • Necrotizing fasciitis is a clinical diagnosis.
    • The hallmark is pain out of proportion to findings. The clinician should have a high level of suspicion and low threshold for surgical consultation in cases of severe pain, swelling, and fever. Furthermore, the physician should have a high index of suspicion for patients who present with severe pain in an anatomic area, with no other cause; necrotizing fasciitis may have severe pain as the ONLY symptom early on in the presentation.
    • Early necrotizing fasciitis may present with no marks/lesions on the skin, and non-specific symptoms.
    • Necrotizing fasciitis may follow minor trauma to the skin or varicella skin infection. A high index of suspicion is essential.  Blood tests (elevated WBC, C-Reactive Protein, or CK) are non-specific. Typical labs drawn are CBC, eclectrolytes, BUN, CR (GFR), C Reactive Protein, INR, LFTs and an ECG.
    • Presence of bullae or gas in tissue (see images below) is a late finding with the latter usually only seen in Type III necrotizing fasciitis.
    • Plain xrays can also be done but have poor sensitivity.
    • MRI has reasonable sensitivity for detecting necrotizing fasciitis, but surgical consultation should not be delayed for imaging for suspected necrotizing fasciitis. It is better to refer early, and have it be a false positive!


    Quality Of Evidence?


    Because of the rarity of necrotizing fasciitis, there are few studies to draw on. These are retrospective studies and frequently based on expert opinion.


    Related Information


    1. Necrotizing Fasciitis  (St Paul’s EM Update 2018)

      Presenter: Simon Jones, Clinical Instructor, UBC Department of Emergency Medicine

    Reference List

    Relevant Resources


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    Sepsis and Soft Tissue Infections


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