From the Guidelines
POCUS has a high specificity of 93.3% for diagnosing necrotizing fasciitis, as demonstrated in a prospective observational study of 62 patients with clinically suspected necrotizing fasciitis. This means that when POCUS shows findings consistent with necrotizing fasciitis, it is likely to be accurate. The key sonographic findings include diffuse subcutaneous thickening accompanied by fluid accumulation of > 4 mm in depth along the deep fascial layer, which are predictive of necrotizing fasciitis 1.
Key Findings
- POCUS can be performed rapidly at bedside without delaying surgical intervention, which remains the definitive treatment for necrotizing fasciitis.
- The sensitivity of POCUS for diagnosing necrotizing fasciitis is 88.2%, meaning some early cases might be missed 1.
- POCUS should be used as part of a comprehensive evaluation that includes clinical assessment, laboratory values, and potentially other imaging modalities in uncertain cases.
- Other imaging modalities, such as CT and MRI, may also be useful in diagnosing necrotizing fasciitis, but POCUS has the advantage of being rapidly performed at bedside.
Clinical Implications
- POCUS should be used to support clinical diagnosis and guide surgical intervention in cases of suspected necrotizing fasciitis.
- A combination of clinical assessment, laboratory values, and imaging modalities, including POCUS, should be used to diagnose necrotizing fasciitis.
- Early diagnosis and treatment of necrotizing fasciitis are critical to improving patient outcomes and reducing morbidity and mortality.
From the Research
POCUS Necrotizing Fasciitis Specificity
- The specificity of POCUS for diagnosing necrotizing fasciitis ranged from 44.7% to 98.2% in a systematic review of the literature 2.
- Subcutaneous emphysema was found to be the most specific sign for necrotizing fasciitis, with a specificity of 100% (95% CI 92.5% - 100%) 2.
- A prospective study found that POCUS had a high sensitivity and specificity for identifying necrotizing fasciitis, with all high-risk patients having POCUS images concerning for NF, and all but one low-risk patient having POCUS images not concerning for NF 3.
- Another study reported a case of necrotizing fasciitis diagnosed with POCUS, which was missed by computed tomography and magnetic resonance imaging, highlighting the potential utility of POCUS in diagnosing NF 4.
- The use of POCUS in diagnosing necrotizing fasciitis is supported by its ability to identify fluid accumulation along the fascial plane and other signs of NF, such as thickened deep fascia and fluid pockets 2, 4, 3.