From the Guidelines
POCUS power Doppler is a valuable tool in the early diagnosis of necrotizing fasciitis, allowing for rapid assessment and differentiation from cellulitis at the bedside. When evaluating suspected necrotizing fasciitis, power Doppler can detect areas of decreased blood flow in the affected tissues, which is characteristic of the disease due to thrombosis of blood vessels and tissue necrosis 1. The technique involves using a high-frequency linear transducer placed over the area of concern, with power Doppler settings optimized to detect low-flow states. Findings suggestive of necrotizing fasciitis include subcutaneous thickening, fascial fluid, fascial irregularity, and most importantly, decreased or absent blood flow in the affected tissues compared to adjacent normal areas.
Key Findings and Recommendations
- POCUS power Doppler should be used as part of a comprehensive assessment including clinical examination and laboratory tests, such as the Laboratory Risk Indicator for Necrotizing infection (LRINEC) score, although recent evidence has demonstrated that the LRINEC score lacks sensitivity for the early diagnosis of necrotizing infections 1.
- The diagnosis of necrotizing infection is primarily a clinical diagnosis, and imaging studies should not delay surgical consultation and intervention 1.
- Ultrasound, including power Doppler, has the advantage of being rapidly performed at bedside and may be helpful in differentiating simple cellulitis from necrotizing fasciitis, with a sensitivity of 88.2% and specificity of 93.3% in one prospective observational study 1.
- Early surgical intervention is crucial for survival in necrotizing fasciitis, and the use of POCUS power Doppler can aid in rapid diagnosis and management, potentially improving outcomes by reducing delays in definitive treatment.
Clinical Application
In clinical practice, the use of POCUS power Doppler for the diagnosis of necrotizing fasciitis should be considered as part of a multifaceted approach, including clinical evaluation, laboratory tests, and other imaging modalities as needed. The ability to perform power Doppler at the bedside allows for immediate assessment and can help guide decision-making regarding the need for surgical intervention, which is critical for patient outcomes in necrotizing fasciitis.
From the Research
POCUS Power Doppler in Necrotizing Fasciitis
- The use of Point-of-Care Ultrasound (POCUS) with power Doppler has been studied as a diagnostic tool for necrotizing fasciitis (NF) 2, 3.
- POCUS has been shown to have high sensitivity and specificity in identifying NF, with fluid accumulation along the fascial plane being a sensitive finding and subcutaneous emphysema being a specific finding 3.
- The use of POCUS can aid in the early diagnosis of NF, allowing for prompt treatment and reducing the risk of complications 2, 3.
- Power Doppler can help identify increased blood flow to the affected area, which can be indicative of inflammation and infection 4.
- While POCUS is a useful diagnostic tool, it should be used in conjunction with clinical evaluation and other diagnostic tests, such as laboratory findings and imaging studies, to confirm the diagnosis of NF 2, 4, 5.
Diagnostic Findings
- Fluid accumulation along the fascial plane is a sensitive finding for NF, with a sensitivity of 85.4% (95% CI 72.2% - 93.9%) 3.
- Subcutaneous emphysema is a specific finding for NF, with a specificity of 100% (95% CI 92.5% - 100%) 3.
- Thickening of the deep fasciae due to fluid accumulation and reactive hyperemia is a characteristic finding of NF, best seen on magnetic resonance imaging 4.