What are the specific Point-of-Care Ultrasound (POCUS) findings for necrotizing fasciitis?

From the Guidelines

POCUS findings specific for necrotizing fasciitis include thickened fascial planes (>4mm), subcutaneous emphysema (air) appearing as hyperechoic foci with dirty shadowing, fascial fluid collections, and subcutaneous edema with a "cobblestone" appearance, as demonstrated in a prospective observational study of 62 patients with clinically suspected necrotizing fasciitis, which found that ultrasound had a sensitivity of 88.2% and specificity of 93.3% 1.

Key POCUS Findings

• Thickened fascial planes (>4mm)
• Subcutaneous emphysema (air) appearing as hyperechoic foci with dirty shadowing
• Fascial fluid collections
• Subcutaneous edema with a "cobblestone" appearance
• The STAFF sign (Subcutaneous Thickening, Air, and Fascial Fluid) is particularly indicative of necrotizing fasciitis

Importance of POCUS in Necrotizing Fasciitis

• POCUS can be performed rapidly at bedside without delaying surgical intervention, which remains the definitive treatment 1
• The presence of subcutaneous gas is highly specific but not always present, especially in early disease
• POCUS findings should be integrated with clinical assessment, as early necrotizing fasciitis may have subtle or absent ultrasound findings despite severe infection

Technical Considerations for POCUS

• Use a high-frequency linear transducer (7-15 MHz)
• Compare with the contralateral unaffected side to better appreciate abnormalities
• Power Doppler may show hyperemia in surrounding tissues but decreased or absent blood flow in necrotic areas, as noted in the study by Sartelli et al. 1

From the Research

POCUS Necrotizing Fasciitis Specific Findings

• The use of Point-of-Care Ultrasound (POCUS) in diagnosing necrotizing fasciitis has been evaluated in several studies 2, 3.
• POCUS has been found to have a high sensitivity and specificity for the diagnosis of necrotizing fasciitis, with fluid accumulation along the fascial plane being the most sensitive finding (85.4%; 95% CI 72.2% - 93.9%) 3.
• Subcutaneous emphysema was found to be the most specific finding (100%; 95% CI 92.5% - 100%) 3.
• A study published in The American Journal of Emergency Medicine found that POCUS can be used to identify necrotizing fasciitis with a high sensitivity and specificity, and that it can be a useful adjunct to clinical decision making 2.
• The findings of these studies suggest that POCUS can be a valuable tool in the diagnosis of necrotizing fasciitis, particularly in the emergency department setting 2, 3.

Diagnostic Criteria

• The diagnosis of necrotizing fasciitis relies on clinical symptoms and signs, laboratory markers, and imaging, with the gold standard for diagnosis being intraoperative tissue culture 4.
• POCUS can be used to identify specific findings associated with necrotizing fasciitis, including fluid accumulation along the fascial plane and subcutaneous emphysema 3.
• The use of POCUS in conjunction with clinical evaluation and other diagnostic modalities can help to improve the accuracy of diagnosis and guide treatment decisions 2, 3.

Treatment and Management

• The treatment of necrotizing fasciitis involves prompt surgical debridement of necrotic tissues, intravenous antibiotics, and supportive care 4, 5.
• Adjuvant therapies, such as intravenous immunoglobulin and hyperbaric oxygen therapy, may also be used in the treatment of necrotizing fasciitis, although their efficacy has not been rigorously established 4, 5.
• The use of POCUS in the diagnosis of necrotizing fasciitis can help to facilitate prompt treatment and improve outcomes 2, 3.