Correspondence and reprint requests to:
Dr. Masanori Kawataki
Department of Respiratory Medicine, Ohara Healthcare Foundation, Kurashiki Central Hospital, 1-1-1 Miwa, Kurashiki, Okayama 710-8602, Japan
E-mail:masanori19881027@gmail.comKeywords: Necrotizing soft tissue infection, Muscle necrosis
Key clinical message
Necrotizing Soft Tissue Infection can be challenging to differentiate from abscesses based on computed tomography imaging findings only, so it is crucial to perform surgical debridement as early as possible.
Case report
A 72-year-old male presented to our hospital with left hip joint pain and general fatigue for four days. He had a medical history of erythroderma and was taking prednisolone 5 mg. The examination revealed pain in the left hip joint during passive movement. Contrast-enhanced computed tomography (CT) showed low attenuation in the left adductor muscle group. No fluid retention or increased fat tissue density was observed (Figure 1). Intramuscular abscess was suspected, and surgical debridement was performed. Surgical debridement revealed cloudy exudate in the superficial fascia and synovial sac. The diagnosis of Necrotizing Soft Tissue Infection (NSTI) was subsequently confirmed.
NSTI on CT show typically gas along the fascia plane, fat stranding, increased density, edema and thickening of the fascia, obscure appearance of the fascial surface, non-enhancement of fascia, and fluid retention. Meanwhile, CT findings of muscle necrosis show low attenuation and are also associated with muscle edema1.
In the abscess, fluid attenuation on CT is a collection circumscribed by an enhanced, irregular, thin wall. Moreover, the surrounding tissue can develop edema and a low-density area1. Therefore, it is difficult to distinguish an NSTI from an abscess based on CT imaging findings alone when the findings are not typical.
Source control improves mortality in NSTI2, and surgical findings can confirm the diagnosis3. Conducting a surgical consultation as early as possible is critical if the imaging findings are not typical. In this case, Methicillin-resistant Staphylococcus aureus was detected in joint fluid and tissue cultures. Antibiotic therapy was continued for approximately 12 weeks, and he was transferred to another hospital for rehabilitation.
References
  1. Chang CD, Wu JS. Imaging of Musculoskeletal Soft Tissue Infection. Semin Roentgenol. 2017;52(1):55-62.
  2. Martínez ML, Ferrer R, Torrents E, et al. Impact of Source Control in Patients With Severe Sepsis and Septic Shock. Crit Care Med. 2017;45(1):11-19.
  3. Pelletier J, Gottlieb M, Long B, Perkins JC Jr. Necrotizing Soft Tissue Infections (NSTI): Pearls and Pitfalls for the Emergency Clinician. J Emerg Med. 2022;62(4):480-491.