Importance: Necrotizing fasciitis is a relatively uncommon and potentially life-threatening soft tissue infection, with morbidity and mortality approaching 25% to 35%, even with optimal treatment. The challenge of diagnosis for necrotizing soft tissue infections (NSTIs) is their rarity, with the incidence of approximately 1000 cases annually in the United States. Given the rapid progression of disease and its similar presentation to more benign processes, early and definitive diagnosis is imperative. Findings: Signs and symptoms of NSTIs in the early stages are virtually indistinguishable from those seen with abscesses and cellulitis, making definitive diagnosis difficult. The clinical presentation will depend on the pathogen and its virulence factors which ultimately determine the area and depth of invasion into tissue. There are multiple laboratory value scoring systems that have been developed to support the diagnosis of an NSTI. The scoring system with the highest positive (92%) and negative (96%) predictive value is the laboratory risk indicator for necrotizing fasciitis (LRINEC). The score is determined by 6 serologic markers: C-reactive protein (CRP), total white blood cell (WBC) count, hemoglobin, sodium, creatinine, and glucose. A score ≥ 6 is a relatively specific indicator of necrotizing fasciitis (specificity 83.8%), but a score <6 is not sensitive (59.2%) enough to rule out necrotizing fasciitis. In terms of imaging, computed tomography (CT) imaging, while more sensitive (80%) than plain radiography in detecting abnormalities, is just as nonspecific. Computed tomography imaging of NSTIs demonstrates fascial thickening (with potential fat stranding), edema, subcutaneous gas, and abscess formation. Magnetic resonance imaging (MRI) has demonstrated sensitivity of 100% and specificity of 86%, though MRI may not show early cases of fascial involvement of necrotizing fasciitis. Conclusions and Relevance: Necrotizing soft tissue infections are rapidly progressive and potentially fatal infections that require a high index of clinical suspicion to promptly diagnose and aggressive surgical debridement of affected tissue in order to ensure optimal outcomes. Prompt surgical and infectious disease consultation is necessary for the treatment and management of these patients. While imaging is useful for further characterization, it should not delay surgical consultation. Necrotizing soft tissue infection remains a clinical diagnosis, although plain radiography, CT imaging, and ultrasound can provide useful clues. In general, the management of these patients should include rapid diagnosis, using a combination of clinical suspicion, laboratory data (LRINEC score), and imaging (MRI being the recommended imaging modality), prompt infectious disease and surgical consultation, surgical debridement, and delayed reconstruction. Laboratory findings that can more strongly suggest a diagnosis of NSTI include elevated CRP, elevated WBC, low hemoglobin, decreased sodium, and increased creatinine. Imaging findings include fascial thickening (with potential fat stranding), edema, subcutaneous gas, and abscess formation. Broad-spectrum antibiotics should be started in all cases of suspected NSTI. Surgical debridement, however, remains the lynchpin for treatment of cervical necrotizing fasciitis.
Executive Summary: Practice Guidelines for the Diagnosis and Management of
Skin and Soft Tissue Infections: 2014 Update by the Infectious Diseases Society of
America