The topic of necrotizing fasciitis has been extensively explored on the Chief’s Blog, and today we are looking into whether CT is a good test for ruling out (i.e. has a high sensitivity) for necrotizing fasciitis. In the evernote below, I have integrated some of the prior nec fasc postings and included this update.
Sensitivity of CT for Necrotizing Soft Tissue Infections:
In a single-site study at MGH, published in Archives of Surgery
- Patient with suspicion of necrotizing skin/soft tissue infection (NSTI) but who did not have obvious NSTI (those people were taken straight to OR).
- CT scan findings (specifically 1.) asymmetric and diffuse areas of soft tissue inflammation and ischemia, 2.) muscle necrosis, 3.)gas across tissue planes, and 4.) fluid collections) compared to surgical findings.
- 85 patients with suspected NSTI (18 directly taken to OR),
- leaving 67 patients to undergo CT prior to surgical exploration
- 58 (87%) underwent surgical exploration
- 25 (37% of all patients and 43% of those who underwent surgical exploration) had confirmed NSTI
- 33 had non-NSTIs and did not require debridement or had an isolated abscess + 9 more who were medically managed
- All patients has their NSTI correctly diagnosed by CT scanning (met one of the four criteria for NSTI), there were no false-negative test results.
- There were 8 (19%) false-positives
- Ultimately, the sensitivity was 100%, Specificity 81%, PPV 76%, NPV 100%
- In 1 patient, the first scan was equivocal and had to be repeated 12 hours later, this would be debatable as an actual false-negative
- The CT findings most commonly found were asymmetric and diffuse areas of soft tissue inflammation and fluid collection, this can be conflated with a polymyositis
- This was a single-site study with a relatively small number of patients
- Zacharias N et al. 2010. Diagnosis of necrotizing soft tissue infections by computed tomography. Arch Surg. 145(5):452-455
- Necrotizing Fasciitis: https://www.evernote.com/shard/s509/sh/cce19b1a-fc5c-45a7-86cb-9e54dc1f9a98/7fbff7dd08ec869667e9485deb267cb1