11.10 Cutaneous Abscess or Pustule
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agk's Library of Common Simple Emergencies

Presentation
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With or without a history of minor trauma (such 
as an embedded foreign body) the patient has 
localized pain, swelling and redness of the skin. 
The area is warm, firm, and, usually fluctuant to 
palpation. There is sometimes surrounding 
cellulitis or lymphangitis and, in the more 
serious case, fever. There may be an spot where 
the abscess is close to the skin, the skin is 
thinned, and pus may break through to drain 
spontaneously ("pointing"). A pustule will appear 
only as a cloudy tender vesicle surrounded by 
some redness and induration, and occasionally 
will be the source of an ascending lymphangitis.

What to do:
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- A pustule may not require any anesthesia for 
    drainage. Simply snip open the cutaneous roof 
    with fine scissors or an inverted #11 blade, 
    grasp an edge with pickups and excise the 
    entire overlying surface. Cleanse the open 
    surface with normal saline and cover it with 
    povidone-iodine ointment and a dressing.
- When the location of an abscess cavity is 
    uncertain, attempt to aspirate it with a #18 
    gauge needle after prepping the area with 
    povidone-iodine. If an abscess cavity cannot 
    be located, send the patient out on 
    antibiotics and intermittent warm moist 
    compresses and have him seen again in 24 
    hours.
- When the abscess is pointing or has been 
    located by needle aspiration, prepare the 
    overlying skin for incision and drainage with 
    povidone-iodine solution. Anesthetize the 
    area with regional field block, accomplished 
    by injecting a ring of subcutaneous 1% 
    lidocaine solution approximately l cm away 
    from the erythematous border of the abscess. 
    In addition, inject lidocaine into the roof 
    of the abscess along the line of the 
    projected incision.
- The incision should be made with a #11 or #15 
    blade at the most dependent area of 
    fluctuance. It should be large and directed 
    along the relaxed skin tension lines to 
    reduce future scarring.
- In larger abscesses insert a hemostat into the 
    cavity to break up any loculated collections 
    of pus. The cavity may then be irrigated with 
    normal saline and loosely packed with 
    Iodoform or plain gauze. Leave a small wick 
    of this gauze protruding through the incision 
    to allow for continued drainage and easy 
    removal after 48 hours.
- The patient should be instructed to use 
    intermittent warm water soaks or compresses 
    for a few days when there is no packing used 
    or after packing is removed.
- A dressing should be provided to collect 
    continued drainage.

What not to do:
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- Do not incise an abscess that lies in close 
    proximity to a major vessel, such as in the 
    axilla, groin or antecubital space, without 
    first confirming its location and nature by 
    needle aspiration.
- Do not treat deep infections of the hands as 
    simple cutaneous abscesses. When significant 
    pain and swelling exists, or there is pain or 
    range of motion of a finger, seek surgical 
    consultation.

Discussion
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Either trauma or obstruction of glands in the 
skin can lead to cutaneous abscesses. Incision 
and drainage is the definitive therapy for these 
lesions and, therefore, routine cultures and 
antibiotics are generally not indicated. 
Exceptions exist in the immunologically 
suppressed patient, the toxic, febrile patient, 
or where there is a large area of cellulitis or 
lymphangitis, in which cases an antibiotic can be 
selected on the basis of a Gram stain or 
presumptively based on body location.

It is sometimes not possible to achieve total 
regional anesthesia for incision and drainage of 
an abscess, perhaps because local tissue acidosis 
neutralizes local anesthetics. In such cases, 
additional analgesia may be obtained by 
premedication with narcotics or brief inhalation 
of nitrous oxide.

References:
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Llera JL, Levy RC: Treatment of cutaneous 
abscess: a double-blind clinical study. *Ann 
Emerg Med* 1985;14:15-19.

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