It has been long held dogma that one should irrigate the abscess cavity after ED incision and drainage. But as these authors point out, there is no high quality evidence to support this practice.
Unfortunately, this is still the case.
This RCT was conducted in Fresno, California; better known as MRSA country. They enrolled 209 patients with all kinds of abscesses to irrigation vs. no irrigation. This pragmatic design allowed for packing and antibiotics at the discretion of the doctor.
The primary outcome was ‘further intervention’ as defined by repeat I&D, antibiotic change or abscess related hospital admission.
Results? No difference with 15% vs. 13% meeting the primary outcome in the irrigation vs. no irrigation group respectively.
So, we should stop irrigating abscesses!?
Unfortunately, the jury is still out...
This was a small underpowered study with heterogeneous patient population. I don’t think we can make conclusions about the larger pus pockets with lots of necrotic material.
The irrigation was pretty half hearted. This was not standardized and the authors suggest about 100ml was used. Therefore, it is not surprising that such a minor intervention resulted in no difference. Perhaps more aggressive efforts would have achieved better outcomes? Once again, who knows?
Usually randomization evens out the confounders, but for some reason the irrigation group got more packing. In addition, they got more antibiotics at 90% vs. 72% of the time! That’s a lot of antibiotics for cutaneous abscesses and certainly not reflective of my practice (low MRSA prevalence).
The determination of the primary outcome was by 30 day telephone interview. This is far from perfect and could have led to some miscalls. This is better known as non-differential misclassification that can dilute the results towards the null hypothesis. Put another way, this could have watered things down (no pun intended).
The Annals of EM editors capsule summary concludes, “Irrigation of abscesses appears unnecessary after incision and drainage.” I guess this all depends on how you interpret ‘appears.’
In summary, this was a small study that still leaves us with more questions than answers. It gets points for originality. Maybe it's right, but unfortunately we are still in a necrotic mess.
Chinnock, B, Hendy GW, Irrigation of Cutaneous Abscesses Does Not Improve Treatment Success. Ann Emerg Med. 2016;67:379-383.