image by: Tulane University Preventive Medicine Residency Program
There is no set of clinical findings, lab test results and even imaging that can definitively rule out necrotizing fasciitis – an infection of the deep soft tissues that rapidly spreads along fascial planes and carries a mortality of 30-40%, even with therapy. If you have anything more than the slightest suspicion based on your clinical exam, consider early consultation with a plastic surgeon and start empiric antibiotics. While lab findings and imaging findings can be supportive of the diagnosis, negative lab and imaging studies cannot rule out necrotizing fasciitis and should never override clinical judgment. When lab tests and imaging are noncontributory, the diagnosis can only be made…
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Necrotizing fasciitis can present insidiously with nonspecific symptoms and minimal skin findings.
This meta-analysis demonstrates that diagnosis of necrotizing fasciitis is difficult and the tools we have as Emergency Physicians do not have the best diagnostic accuracy to be able to rule out necrotizing fasciitis on their own given low sensitivities. CT scan looking for fascial edema or enhancement or gas appears to have the highest sensitivity of 94.3%. However, there is still room for error and a negative CT scan does not definitively exclude necrotizing fasciitis.
So, why might it be that the LRINEC score has not proven to be a robust and reliable indicator of necrotizing fasciitis?
First, it is important to recognize what the components of LRINEC are really indicating – systemic derangement. These laboratory criteria are signatures of critical illness and severe sepsis. Early cases of necrotizing fasciitis may not yet demonstrate significant laboratory abnormalities, as patients’ disease has not yet progressed to that stage.
If high suspicion for necrotizing fasciitis through clinical history and physical exam, do not calculate a LRINEC score and go straight to operative debridement. Note: Use with caution, as the LRINEC Score has performed poorly in external validation, most recently in Neeki 2017.
The diagnosis of necrotizing soft tissue infection is ultimately made upon visual examination of necrotic appearing tissue in the operating room. A general paucity of cutaneous findings early in disease progression can make diagnosis difficult,
Consider necrotizing fasciitis in patients with concerning findings for serious soft tissue infections and risk factors. Purposefully attempt to rule out the condition by a careful examination and scrutiny of laboratory indicators.
Diagnosis of NF can be particularly challenging as early signs can be difficult to distinguish from less harmful soft tissue infections such as cellulitis. It most often presents over the time course of hours and can lead to rapid tissue destruction, systemic illness, and death if not promptly recognized and intervened upon.
Necrotizing infections are life-threatening, prompt recognition is key, and POCUS is a useful adjunct to clinical assessment, especially in unstable patients that you don't want to send out of the ED for imaging. It's generally a better rule in (than rule out) test but evidence is limited.
Relying on the absence of skin necrosis, cutaneous anesthesia, gas formation, and bullae to rule out NF can be dangerous. Subcutaneous emphysema has been traditionally stressed as the classic finding of NF, but only gas-forming organisms produce this finding, and it is only present between 13-31% of the time.
Unfortunately, due to the rarity of the disease as well as the fact that diagnosis is made in the operative theater, delay in diagnosis is common. These infections remain elusive, however, due to their relative rarity and similarity to other, more benign conditions.
Computed tomography (CT) has superior sensitivity compared with radiography for the diagnosis of necrotizing soft tissue infection, although different imaging findings have various diagnostic test characteristics. No single element of the physical examination, radiography, or the Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score has sufficient sensitivity to exclude necrotizing soft tissue infection.
Necrotizing fasciitis may appear like cellulitis, but alternatively may have little if any redness. Skin findings may be scant as these skin findings represent “the tip of the iceberg” of the tissue destruction in the deep tissues. Streaking lymphangitis favours the diagnosis of cellulitis over necrotizing fasciitis.
Don't get hung up on subcutaneous gas and late findings of necrotizing fasciitis (e.g., bullae, necrosis). Pain out of proportion to exam is usually the key early finding.
Meropenem 1g or 25mg/kg Q8 hrly + Clindamycin 600mg or 15mg/kg Q8h
Led by Aimee Copeland, a licensed master social worker with a background in eco-psychology, a quadruple amputee and a necrotizing fasciitis survivor, ACF inspires hope through action, builds community through inclusivity, provides healing through relationships, fights stigma through education, and breaks down barriers through compassion and humor.
The Necrotizing Fasciitis Foundation was created by survivors as a way to provide support and resources for NF victims and their families, and to raise awareness by educating the general public and the medical community.