What are the findings of Point-of-Care Ultrasound (POCUS) with color Doppler in necrotizing fasciitis?

From the Guidelines

Color Doppler ultrasound is a valuable POCUS tool for evaluating suspected necrotizing fasciitis, showing decreased or absent blood flow in affected tissues, with a sensitivity of 88.2% and specificity of 93.3% 1. When performing this exam, use a high-frequency linear transducer (7-15 MHz) to assess the area of concern, first in B-mode to identify fluid collections, fascial thickening (>4mm), and subcutaneous emphysema, then activate Color Doppler to evaluate perfusion. Key findings in necrotizing fasciitis include:

• Hyperechoic foci with reverberation artifacts (gas)
• Characteristic "dirty shadowing" appearance
• Lack of blood flow in the deep fascia and subcutaneous tissues when using Color Doppler, reflecting the thrombosed vessels and tissue necrosis characteristic of this condition. This finding helps differentiate necrotizing fasciitis from cellulitis, which typically shows hyperemia (increased blood flow). When performing the exam, apply minimal probe pressure to avoid compressing small vessels and creating false-negative results. Remember that POCUS findings should be integrated with clinical assessment, as early necrotizing fasciitis may have subtle sonographic findings, and surgical consultation should never be delayed if clinical suspicion remains high despite equivocal ultrasound results 1. It is essential to note that imaging studies, including POCUS, should not delay surgical consultation and intervention 1. In cases where the diagnosis is uncertain, a combination of clinical evaluation, laboratory tests, such as the Laboratory Risk Indicator for Necrotizing infection (LRINEC) score, and imaging studies can aid in the diagnosis of necrotizing fasciitis 1. However, the diagnosis of necrotizing infection is primarily a clinical diagnosis, and early surgical consultation and intervention are crucial to improve outcomes in patients with suspected necrotizing fasciitis 1.

From the Research

POCUS and Necrotizing Fasciitis

• Point-of-care ultrasound (POCUS) is a valuable tool in the diagnosis of necrotizing fasciitis (NF), with studies showing high sensitivity and specificity 2, 3.
• The use of color Doppler in POCUS for NF diagnosis is not explicitly mentioned in the provided studies, but the overall accuracy of POCUS in diagnosing NF is supported by the literature.
• A systematic review of the literature found that POCUS has good sensitivity and specificity for the diagnosis of NF, with fluid accumulation along the fascial plane being the most sensitive finding and subcutaneous emphysema being the most specific finding 3.

Diagnostic Findings

• The diagnosis of NF 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 NF with a high sensitivity and specificity, and can be considered as an adjunct to the initial clinical decision making for the diagnosis of NF 2, 3.
• Other diagnostic methods, such as magnetic resonance imaging and frozen section biopsies, have been reported to be of value in the early recognition of NF, but availability and cost limit their routine use 5.

Treatment and Management

• Treatment of NF involves repeated surgical debridement of necrotic tissues in addition to intravenous antibiotics, with adjuvant therapies such as intravenous immunoglobulin (IVIG) and hyperbaric oxygen therapy (HBOT) potentially playing a role 4.
• Prompt diagnosis and proper medical and surgical management of NF are crucial to improve outcomes, with delayed recognition being a deadly pitfall in the management of the disease 5.