What is the role of Point-of-Care Ultrasound (POCUS) with power Doppler in diagnosing necrotizing fasciitis?

From the Guidelines

Power Doppler ultrasound in point-of-care ultrasound (POCUS) is a valuable tool for diagnosing necrotizing fasciitis, and its use is recommended in unstable patients to differentiate simple cellulitis from necrotizing fasciitis, as stated in the 2018 WSES/SIS-E consensus conference recommendations 1.

Key Findings

• The diagnosis of necrotizing infection is primarily clinical, but radiologic imaging, including ultrasound, can provide useful information when the diagnosis is uncertain 1.
• Ultrasound 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 a prospective observational study of 62 patients 1.
• The findings of diffuse subcutaneous thickening accompanied by fluid accumulation of > 4 mm in depth along the deep fascial layer are predictive of necrotizing fasciitis 1.

Recommendations for POCUS

• Use a high-frequency linear transducer (7-15 MHz) for superficial tissues to assess blood flow patterns in the affected tissues.
• Apply minimal probe pressure to avoid compressing small vessels and adjust Doppler gain settings to optimize flow detection.
• Look specifically for subcutaneous thickening greater than 4mm, fascial fluid accumulation, and areas of decreased or absent blood flow which indicate tissue necrosis.

Importance of Early Detection

• Early detection using power Doppler ultrasound can expedite surgical consultation and intervention, potentially improving outcomes in this condition with high mortality rates.
• Imaging studies, including ultrasound, should not delay surgical consultation and intervention, as stated in the 2018 WSES/SIS-E consensus conference recommendations 1.

From the Research

POCUS in Necrotizing Fasciitis Diagnosis

• Point-of-care ultrasound (POCUS) can be used to identify necrotizing fasciitis (NF) with a high sensitivity and specificity 2.
• POCUS images of the suspected site of infection can be obtained by the emergency medicine physician and interpreted based on sonographic findings of NF 2.
• The use of POCUS can aid in the early diagnosis of NF, allowing for prompt surgical debridement and treatment 2.

Power Doppler in POCUS

• While the provided studies do not specifically mention the use of power Doppler in POCUS for NF diagnosis, power Doppler is a technique used in ultrasound to detect blood flow and can be useful in evaluating the vascular supply to the affected tissue.
• The use of power Doppler in POCUS may help identify areas of decreased blood flow, which can be indicative of NF 2.

Diagnostic Modalities for Necrotizing Fasciitis

• Imaging tests, such as computed tomography (CT) scans and magnetic resonance imaging (MRI), can be used to confirm the diagnosis of NF and assess the extent of the disorder 3.
• Laboratory findings, bedside tests, and biopsy can also be helpful in the early recognition of NF 3.
• The gold standard for diagnosis remains intraoperative tissue culture 4.

Treatment and Management

• Urgent surgical debridement is the mainstay of treatment in all patients with NF 5, 6, 4.
• Repeated surgical debridement of necrotic tissues, in addition to intravenous antibiotics, is necessary for the management of NF 5, 4.
• Adjuvant therapies with intravenous immunoglobulin (IVIG) and hyperbaric oxygen therapy (HBOT) may have a role in the treatment of NF 4.