Diagnosis of an abscess is generally made by observation of a tender, warm, fluctuant mass on physical examination.
Fluctuance can be described as a tense area of skin with a wave-like or boggy feeling upon palpation this is the pus which has accumulated beneath the epidermis.
Without adequate evacuation of this pus, the infection will continue to accumulate and can lead to disseminated or systemic infection.
Because there may be surrounding cellulitis, induration can make an abscess less apparent on physical exam. In these cases, bedside ultrasound can be helpful in differentiating a simple cellulitis from an abscess which requires drainage.
When reviewing ultrasound, areas of cellulitis are hyperechoic with thickened lobules of subcutaneous fat interwoven with hypoechoic strands of fluid this is referred to as “cobblestoning.”
In contrast, abscesses have a better-defined collection of anechoic fluid sometimes containing loculations and whirling debris. There may be overlying findings of cellulitis or a hyperechoic rim.
If there is a localized area of induration but no fluctuance found on doing an examination or fluid collection found on doing an ultrasound, home care with the application of heat via warm compresses or soaks along with antibiotics may be attempted.
However, it may be the very early development of an abscess which will be ready to drain within 24-36 hours, so these patients should be well educated on the signs of abscesses and reasons to return to the ER for re-evaluation.
There are few contraindications to this procedure however, certain situations should prompt consideration of consultation of general or specialty surgical services: large or complex abscesses, those in sensitive areas (face, hand, breast and genitalia) or in regions in close proximity to structures such as blood vessels.
Abscesses that do not resolve despite repeated adequate drainage should prompt consideration of a retained foreign body, underlying osteomyelitis or septic arthritis, unusual organisms such as fungi or mycobacteria, or immunodeficiency of the patient (i.e.: uncontrolled or undiagnosed diabetes).
Occasionally, needle aspiration may be attempted by the Emergency Physician or subspecialist with a smaller abscess in these situations.
However, the success rate of needle aspiration is lower for multiple reasons: the inability to aspirate pus does not necessarily mean there is no purulence to be drained and some will later require repeat drainage (either again by needle or later by I&D.)
Prepare the skin by cleaning with alcohol swabs, betadine or chloraprep.  Clean gloves and sterile equipment should be used, though this is a procedure that is impossible for sterility to be maintained (given the draining of infected contents.)
Prophylactic antibiotics are recommended in patients at high risk for infective endocarditis (prosthetic valves, previous endocarditis and certain cases of congenital heart disease or cardiac transplantation.)
Incision & Drainage of abscess
Make a linear incision across the diameter of the fluctuant area, ensuring appropriate depth to have reached the cavity of purulence.
It’s also important to ensure the length of the incision will allow adequate drainage and room to use hemostats this is typically between 2/3rd to the full length of the diameter of the fluctuant area.
After initial drainage of purulence, probe the incision with hemostats, opening them up at varying angles in multiple different directions within the cavity to break up all loculations.
Normal saline is often used via a syringe (which may have an attached angiocatheter or splash-shield) to irrigate the cavity, though current evidence makes this is of questionable benefit.
It is also optional to pack the wound, as this can be a source of increased discomfort for the patient and appears to be of limited utility in the current literature.
However, some emergency physicians still opt to pack larger abscess cavities with the intent of allowing adequate drainage by preventing premature closure in the days following Incision & Drainage.
Thin, continuous, plain or iodoform gauze should be placed gently into the cavity with 2 cm extruding and taped to the skin. It should not be packed tightly as this increases pain for the patient and is not necessary. The wound can then be covered with a dressing.