Tag Archives: perianal abscess

“Choosing wisely bacteriology II: Swabs from the peri-anal area”

There is so much scope for “choosing wisely” in general bacteriology, it is difficult to know where to start…

Peri-anal swabs are rarely of value in changing patient management. That is primarily because you are swabbing an incredibly “dirty” area in the first place. You can be sure that your peri-anal area will almost inevitably grow mixed enteric flora on culture. That is completely normal. It is no reflection on your personal hygiene!

So as a result the following swabs have very dubious microbiology value:

  • Swabs from peri-anal abscesses:- The very fact that you can swab a peri-anal abscess means that it is either self-discharging or has been intentionally incised. Either way the patient should be well on the way to recovery. And you will probably grow mixed enteric flora. On occasion, antibiotics may be indicated if there are systemic symptoms such as a fever, or there is extensive erythema surrounding the abscess. If an antibiotic is used, then it should be necessarily relatively broad spectrum, covering staphylococci, streptococci, anaerobes, and enterobacteraciae. The swab result rarely impacts on the choice of antibiotic.
  • Swabs from sacral ulcers:- This condition has the double whammy of not only being chronic, but is also in the peri-anal region. Rarely, if ever, does a superficial swab from a sacral ulcer change management. A well taken punch biopsy might…

We still accept such swabs at my laboratory, although sometimes I wonder if we are just encouraging poor practice.

Maybe we are just too nice…

We do however put a comment on all such swabs stating the following: “Superficial swabs from the peri-anal area are generally contraindicated. These swabs often grow a mixture of enteric flora, and are unhelpful in making clinical management decisions.”

I like report comments. Unlike one off educational material,  report comments offer continuous feedback to the lab user and can hopefully induce a change in culture over the long term.


“The Bottom Line”

This post continues the “merdish” theme of the previous article. There are two of types of microbiology samples in this area which I have always had some reservations about as to their usefulness. These are samples from peri-anal abscesses and pilo-nidal sinuses.

There a few reasons why I believe that sampling from these areas are of (very) limited usefulness:

  • Samples taken from areas this close to the anus will almost certainly be colonised with enteric flora (no matter how good toilet hygiene is!). Therefore it can be difficult to work out was is pathogenic and what is just there for the sake of it.
  • For both these conditions, the treatment should be primarily surgical, and antibiotic treatment is very much a secondary option.
  • If antibiotics are being used, given the nature and location of perianal abscesses and pilonidal sinuses, anaerobic cover is required. However due to the poor sensitivity of culturing anaerobes from microbiological samples, anaerobes may not necessarily be recovered from the microbiological sample. This should not however change the treatment. I.e Anaerobic cover should not be stopped just because the microbiology result shows “No anaerobes isolated.”

I suspect that the results of microbiology samples from peri-anal abscesses and pilo-nidal sinuses hardly ever changes the management of the patient and I certainly do not encourage such sampling.

I would be keen to know if any laboratory takes a harder line on such sampling and places a disclaimer comment or even rejects these types of sample.