Abscess Gone Wild

A man came into the emergency department one day with concern for a sore /abscess on his back. He said it had been on his upper left back for a number of years. It was reported by a family member that “air” was coming out of it. I had never heard anything like that and was immediately interested.

His vital signs were within normal ranges without any objective indicators of potential sepsis. He was a daily smoker with a history of hypertension, and otherwise in relatively good health.

On physical exam, there was mild fluctuance (the squishy tactile feedback we get when the normal subcutaneous tissue isn’t all that normal) and pointing (an erosion tissue by the abscess as the body tries to naturally drain the infection). There was a moderate erythemic border and the tissue overlying the abscess was mildly warmer than surrounding tissue.

Point-of-care ultrasound was somewhat baffling and returned way more anechoic features than should have been there (black on ultrasound and literally meaning without echo, i.e. nothing was there for the frequency wave to bounce off of and return back back to the ultrasound probe and paint a white picture). So, I ordered the test we all overorder, a CT.

I ordered a CT of the thorax with contrast to evaluate the abscess. Why? because contrast highlights soft tissues and literally contrasts their features more vividly on computed tomography. I did not order a CT angiogram which is what some might think of when we consider a contrasted CT of the chest. I didn’t have any reasons to suspect a problem with his vasculature and an angiographic study wasn’t indicated. I simply ordered a CT chest with contrast.

Here’s what that CT looked like:

Here’s the video with some explanation:

Labs and Surgery

During the time we had obtained the CT (about 1 hour), we had also obtained labs with the following results:

Discussing the Abscess Gone Wild

Concern for necrotizing fasciitis was low based on the LRINEC score of 1 but high based on the overall clinical impression (gas reported to be coming out of the lesion, gas on CT). and I called a general surgeon who took the gentleman to the OR for open drainage. After debridement, the surgeon placed a wound vacuum and continued antibiotic therapy (Zosyn, daptomycin, clindamycin) that had been initiated in the emergency department.

An abscess can form under many circumstances and typically involves the formation of a cavity or space beneath (at least) the dermal layer, extending to a depth which is usually limited by the amount of pus that can accumulate within the space before it becomes too painful for the patient and must be drained or, through erosion secondary to acidic conditions within the wound, spontaneously begins to drain (pointing is a first sign of this likelihood). The pus forms because bacteria that don’t normally occupy the space get trapped there through trauma or just life and begin to colonize. With necrotizing fasciitis, however, this space is less likely to spontaneously drain because the bacteria involved produce a chemical barrage that causes necrosis (total tissue death and breakdown) through fascial layers, often producing gas and pus together.

When you encounter an abscess that looks odd, or a clinical story that’s just out of place, think about obtaining a point of care ultrasound or other non x-ray imaging to further evaluate the abscess. Necrotizing fasciitis is terminal, and quickly, if untreated (sometimes despite treatment). Always have necrotizing fasciitis in your differential and scratch it off first. Remember, when working your differential diagnosis, life and function affecting illnesses of suspicion should be scratched off the list first. To learn more about abscess evaluation and treatment, as well as ultrasound evaluation of skin and soft tissue illnesses, consider taking The Skin Course.