Early Diagnosis of Necrotizing Fasciitis with Soft Tissue Ultrasound

A 32-year-old man presented with left forearm pain for 3 hours prior to coming to the emergency department. He reported being evaluated at an outside hospital 3 days earlier for depression and opiate withdrawal, during which an intravenous catheter was placed in the affected extremity. On physical exam, he was afebrile with stable vital signs. He had point tenderness and erythema over a healed puncture site on the dorsum of his left forearm. There was no fluctuance or crepitus. He did have pain with flexion and extension of the wrist and during passive stretch of the digits. The patient’s laboratory results included a white blood count of 16.7 × 10⁹/L, hemoglobin of 13.7 g/dL, sodium of 135 mmol/L, creatinine of 1.0 mg/dL, glucose of 81 mg/dL, and a C-reactive protein of 6.0 mg/L. His laboratory risk indicator for necrotizing fasciitis (LRINEC) score was 1 (i.e., low risk). A bedside ultrasound was performed (see Video Clip S1, available as supporting information in the online version of this paper), which revealed an echogenic area within the soft tissue casting a gray (“dirty”) shadow suspicious for subcutaneous emphysema (Figure 1). A surgical consult was immediately obtained and a computed tomography (CT) of the extremity was performed just prior to surgery. The findings on CT confirmed the presence of subcutaneous emphysema (Figure 2). In the operating suite, the patient received both volar and dorsal left forearm fasciotomies with debridement of underlying necrotic muscle. The patient eventually recovered full function of the extremity. Cultures from the wound were positive for methicillin-resistant Staphylococcus aureus.

Figure 1.  A longitudinal ultrasound image along the mid portion of the radius showing an echogenic area casting a grayish (“dirty”) shadow in the subcutaneous tissues above the bone. This ultrasound finding is suggestive of subcutaneous emphysema.

Figure 2.  A coronal CT of the left forearm confirming the presence of subcutaneous emphysema.