I saw a patient the other day with a gluteal/perianal swelling consistent with abscess. It looked erythematous, swollen, tender and indurated as a usual abscess would be…roughly 10cm extending from the external anal sphincter into the gluteal area. What made this abscess interesting was that we could feel a small amount of crepitus on exam. Bedside ultrasound was hindered by what appeared to be air (unfortunately I didn’t save the ultrasound!). Here is what appeared on CT imaging of her pelvis:
This is a non-contrast CT because the patient’s creatinine was elevated. However you can see extensive gas formation in the gluteal area. It extended up near the sacrum and rectum. The patient was taken to the operating room for debridement with concerns for necritizing fasciitis. The amount of gas on CT was not anticipated based on physical exam (the patient had only a little bit of crepitus that could have been missed).
Necrotizing fasciitis on imaging shows up as air in the soft tissue. This can be seen on plain films but the extent is better characterized on CT.
A couple learning points from this case:
1. Use ultrasound on your abscesses! You never know what you may find.
2. Crepitus is bad. Even a little bit. Consider a deep, serious infection that could spread rapidly.
3. If Necritizing Fasciitis is suspected: obtain early broad spectrum antibiotics, resuscitation, surgical consultation, and CT imaging for characterization.
Author: Russell Jones, MD