Necrotizing fasciitis is a rapidly progressive skin and soft tissue infection characterized by invasion of deep fascial layers causing diffuse microvascular occlusion and necrosis ¹. 

By etiology, it may be broadly categorized into two groups; type I (polymicrobial), which is typically associated with medical comorbidities (e.g. diabetes, immunosuppression, peripheral vascular disease) and type II (monomicrobial, typically streptococcus/staphylococcus species), which may occur in the absence of any risk factors ².

Surgery and trauma are common precipitants. Presenting signs and symptoms may include swelling, erythema, and pain, which may progress to cutaneous necrosis, bullae formation, and palpable crepitus ³.

While ultimately a clinical diagnosis, imaging plays a crucial role in timely diagnosis and defining the extent of disease. Radiography may be normal in early disease or show nonspecific soft tissue swelling; more advanced disease may demonstrate air tracking along fascial planes. 

CT is highly sensitive in detecting the presence of subcutaneous emphysema and can define the local extent of disease as well as complications pertinent to surgical management. Supportive features include fascial edema, gas tracking along fascial planes, and increased dermal thickness ⁴.

Point of care ultrasound recognition of features of necrotizing fasciitis may augment timely diagnosis. Sonographic features described include ⁵: 

• irregular, echogenic collections with "dirty" posterior acoustic shadowing
• edematous subcutaneous fat with loss of typically organized echotexture
• thickened fascial layers
• fluid collections abutting the deep fascia