Necrotising fasciitis

Last reviewed: March 2020

Last updated: July 2018

Summary

A life-threatening subcutaneous soft-tissue infection that requires a high index of suspicion for diagnosis.

Infection may be polymicrobial in aetiology (type I) due to mixed anaerobic/facultative anaerobic organisms, or due to a single organism (type II), most commonly Streptococcus pyogenes, also called group A streptococcus.

Necrotising fasciitis should be suspected in any patient with a soft-tissue infection accompanied by prominent pain and/or anaesthesia over the infected area, or signs and symptoms of systemic toxicity.

Signs that raise suspicion for necrotising fasciitis include the presence of hypotension and/or elevated creatinine, elevated creatine kinase, elevated C-reactive protein (>124 nanomol/L [13 mg/L]), elevated white blood cell count with marked left shift, and/or low serum bicarbonate.

No laboratory or imaging studies, alone or in combination, are sufficiently sensitive and specific to definitively diagnose or rule out necrotising fasciitis.

An urgent surgical consultation should be obtained as soon as the diagnosis is suspected. Treatment should not be delayed while awaiting microbiological and imaging investigations.

Definitive treatment is surgical debridement, repeated as necessary. Antibiotic therapy is crucial, but is considered adjunctive to surgical management. Empiric antibiotics should cover major bacterial aetiological agents, and group A streptococcal toxin production that can accompany type II necrotising fasciitis.

Definition

Necrotising fasciitis is a life-threatening subcutaneous soft-tissue infection that may extend to the deep fascia, but not into the underlying muscle. The causal organisms may be aerobic, anaerobic, or mixed flora. Two main clinical forms exist. Type I necrotising fasciitis is a polymicrobial infection with an anaerobe such as Bacteroides or Peptostreptococcus and a facultative anaerobe such as an Enterobacteriaceae or non-group A streptococcus.[1][2][3][4][5] Type II necrotising fasciitis is most commonly a monomicrobial infection with Streptococcus pyogenes (group A streptococci).[1][2][3][4][5][6] Other infectious aetiologies may rarely cause a monomicrobial necrotising infection that may be associated with specific exposures or risk factors (e.g., freshwater exposure associated with Aeromonas hydrophila, saltwater exposure or consumption of raw oysters associated with Vibrio vulnificus).