Infectious Disease Compendium


Ubi pus, ibi evacua

Abscesses can occur anywhere in and on humans. And abscesses only make an ID doctors heart grow fonder. Look up the organ that is involved for the peculiars.

But here are some general principles:

Drain the pus. Probably the most important approach. Antibiotics do not drain pus and are not a substitute for I&D. By the way, I am the ID doc, not the I&D doc; that would be the surgeon.

There are multiple reasons that antibiotics alone to fail for abscesses:

  • little penetration of antibiotics as abscesses have no blood supply
  • they are often a sphere, so the least surface area relative to volume, the worst for antibiotic penetration
  • inactivation of antibiotics in the pus environment
  • perhaps most importantly, most bacteria are not dividing in abscesses and most of our antibiotics require dividing organisms to kill them

Get cultures. Duh. It is nice to know what one is trying to kill.

Drain the pus.

S. aureus usually is found alone. S. anginosus group can abscesses all by their lonesome. In many mixed abscesses, such as brain and liver, there are more organisms in the pus by 16S than can be grown. But any bug can make an abscess.

Drain the pus.

Antibiotic endpoint for most abscesses is cure, however you choose to define it.

Drain the pus.

Patient may get transiently worse after draining the abscess. Draining frees up the remaining organsims to divide, we kill them releasing endotoxin and the patients get ill.

Drain the pus.

My rule of thumb based on zero data and years of conformation bias, is that a 1 cm abscess takes three weeks and I add a week for every centimeter.

Drain the pus.

That being said, 2 cm or so is the maximum size that usually can get better without drainage, which can occur.

Drain the pus.

When palpating a superficial abscess, do not lean over it with your mouth open. They can suddenly squirt in the unexpected directions. Ruined a perfectly good tie that way, just stopping short of my open maw.

Drain the pus.

Curious Cases

Relevant links to my Medscape blog

Probably not, but fun to think about

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