An abscess is a walled-off collection of pus. Abscesses that appear in areas of friction or minor trauma such as underneath the belt, the fronts of the thighs, buttocks, groin, and armpits, are called furuncles or carbuncles.
The clinical signs of an abscess are redness, induration, and fluctuance. In general, abscesses need to be incised and drained, I&D, because the chemical reactions in the pus prevent antibiotics from penetrating well into the surrounding tissues.
Induration is a sign of infection. Skin that is indurated is red, inflamed, thickened, and tender. The swelling and thickening of the skin are a result of the infectious process and the skin's response to fighting off the infection.
Fluctuance is an indication of the presence of pus in a bacterial infection. As the skin gets infected redness and induration develop. The immune system works to fight off the bacteria and old, spent white blood cells collect in the skin. Certain chemicals given off by bacteria and white blood cells also accumulate under the skin forming pus. Sometimes the pus leaks out and the lesion drains, but other times the pus is prevented from draining. The skin overlying the pus remains red, but touching this area produces a soft, boggy feel. This boggy feeling is fluctuance. Often fluctuance is surrounded by induration making it even more noticeable.
In general, lesions that are fluctuant need to be incised and drained, I&D, because the chemical reactions in the pus prevent antibiotics from penetrating well into the surrounding tissues
Incision and drainage, or I&D, is a common treatment for skin infections and abscesses. An infection with pus, or abscess, does not heal well on its own or even with antibiotics. The pus must be drained to promote healing.
An I&D is performed by first numbing the area with local anesthetic. Unfortunately local anesthetic is not as effective in an abscess as it is in normal skin. Sometimes an I&D is performed without local anesthetic to reduce the number of sticks. A scalpel is inserted into the skin overlying the pus and the pus is drained. Many abscesses have pockets of pus that must be broken up to release all of the pus.
Sometimes a wick, usually a piece of gauze or gauze tape, is placed in the drained abscess to keep the skin from closing. This allows the wound to continue to drain as it heals from the inside out.