Key Practice Points
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In recent years, there has been a threefold increase in superficial soft tissue infections (SSTI) including abscesses. The rise in community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is behind that increase.
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Abscesses can begin as solid nodules—furuncles—that suppurate and form a pus-filled mass. Abscesses are fluctuant and soft to palpation because of the pus-filled center.
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CA-MRSA is now found in 50% to 80% of abscesses.
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Breast abscesses can be complicated because of the involvement of the occluded periareolar ducts, and they might require consultation for treatment.
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Bartholin’s gland abscesses can be associated with sexually transmitted diseases that need to be treated at the time of drainage.
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Buttock abscesses can be drained by emergency caregivers. Perianal and perirectal abscesses are best managed by consultants.
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The decision to drain an abscess requires the presence of pus. If there is doubt, needle aspiration or ultrasound examination can resolve the issue.
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When pus is not present, the patient is treated with antibiotics that include coverage for CA-MRSA. Treatment continues until the lesion heals or becomes an abscess.
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The most common mistake in abscess drainage is making the incision too small. It should be at least two thirds of the size of the abscess cavity.
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Whereas simple abscesses caused by CA-MRSA will heal with drainage alone, the role of antibiotics has not been completely defined. Coverage is recommended for those with risk factors, which include associated cellulitis, immunosuppression, fever, and so forth.
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After initial incision and drainage, the patient returns in 2 to 3 days for packing removal and reevaluation.
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Uncomplicated, properly drained abscesses, including those caused by CA-MRSA, resolve without antibiotics. Antibiotics are recommended for abscesses with surrounding cellulitis, toxicity, diabetes, immunocompromise, location on the face, and cardiac valve disease.
Cutaneous and other superficial abscesses commonly are diagnosed and treated in emergency departments (EDs). From 1993 to 2005 there was a threefold increase in superficial soft tissue infections (SSTI) presenting to EDs. The increase is largely due to the emergence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA). The majority of abscesses and other SSTIs that present to EDs are now due to CA-MRSA. In some EDs, the rate of CA-MRSA SSTIs exceeds 80%. Although drainage is the key therapeutic intervention for all abscesses, significant differences between types and locations exist and necessitate individualized treatment. Most cases, including those caused by CA-MRSA, can be managed in the ED with routine outpatient follow-up care. A few cases require specialist consultation, however, for possible operative intervention or inpatient management.
Clinical Presentations
Cutaneous Abscesses
A cutaneous abscess is defined as a “localized collection of pus causing a fluctuant soft tissue swelling surrounded by firm granulation tissue and erythema.” Abscesses can begin as furuncles, which are firm, red, tender solid nodules that can become abscesses if not treated with antibiotics. Cutaneous abscesses can occur on any body surface but tend to be more common in certain areas. The most common sites are the head, neck, axillae, and buttock and perineal areas. Carbuncles are deep abscesses, with multiple loculations, that occur at the nape of the neck, chin, back, and thighs.
Any interruption of the protective layers of the skin, even trivial, with subsequent invasion of exogenous or endogenous microflora, can lead to abscess formation. Abscesses can also be the result of an obstruction of the apocrine and sebaceous glands. Sebaceous glands are widely distributed over the body, and apocrine glands are found most commonly in axillae and anogenital regions. These glands frequently form cysts that are prone to abscess formation. CA-MRSA now makes up the majority of soft tissue abscesses, up to 80% depending on the local microbiology. Other organisms include methicillin-sensitive S. aureus (MSSA), Proteus mirabilis , and group A streptococci. It is important to know what the local sensitivities to antibiotics are so that appropriate antibiotics can be selected.
Abscesses caused by CA-MRSA can be characterized by an abscess-like lesion but with a central black eschar. Satellite lesions can also occur. Certain populations are at higher risk for CA-MRSA. They are children, athletes, those who have contact with a CA-MRSA patient, urban underserved individuals, incarcerated people, the military, those with HIV, men who have sex with men, and animal handlers. Studies have shown that simple abscesses without surrounding cellulitis or other complicating factors can be treated with incision and drainage alone. However, the role of antibiotics has yet to be completely defined.
Of special note are abscesses that arise on the upper lip and nose. Infections in these sites drain through the facial and angular emissary veins to the cavernous sinus. As discussed in the following section, antibiotics are indicated in the treatment of these lesions.
Hidradenitis Suppurativa
A common and difficult condition to manage that predisposes to abscess formation is hidradenitis suppurativa, which is a chronic, relapsing, inflammatory involvement of apocrine glands of the axillae and pubic regions. Abscess formation is followed by extensive, excessive scarring. The microbiology of these infections is complex. Coagulase-negative Staphylococcus and S. aureus are the most common organisms. The rate of CA-MRSA has yet to be determined but is highly likely to be causal in some abscesses. Anaerobes are also present. Recurrent abscess formation also predisposes to fistula tracks, skin and subcutaneous induration, and inflammation in various stages of progression. Emergency management is limited to incision and drainage of the discrete abscesses. These patients require long-term care and a program of management best coordinated and administered by specialists (e.g., dermatologists or surgeons). A strong relationship between hidradenitis and smoking has been found, and patients should be strongly encouraged to stop smoking.
Breast Abscesses
Although breast abscesses commonly are associated with the postpartum period, more than 90% occur outside of that period. Postpartum mastitis, which can occur in nursing mothers 2 to 6 weeks after delivery, predisposes to abscess formation. Mastitis is caused by an invasion of S. aureus through sore, abraded nipples. Like other SSTIs, postpartum infections are increasingly a result of CA-MRSA. Other organisms are MSSA, anaerobes, and mixed flora. These patients are often quite sick from extensive local involvement, pain, chills, and fever. Initial treatment of mastitis without abscess includes ice packs, breast support, analgesics, and antistaphylococus antibiotics. Breast feeding can continue and is beneficial.
Nonpuerperal abscesses can occur in superficial and deep tissues of the breast. Superficial abscesses can be cutaneous or periareolar. Periareolar abscesses, the most common breast abscess, arise from occluded ducts and are associated with the multiple organisms listed previously. These abscesses involve mammary and ductal tissue.
Deep breast abscesses are either intramammary or retromammary. As is the case for periareolar abscesses, fluctuance can be difficult to detect. Fluctuance also is difficult to diagnose when overlying cellulitis is deep and extensive. In these cases, needle aspiration or ultrasound may be required to ensure the proper treatment (i.e., incision and drainage). Because of the complexity of breast abscesses, and the frequent involvement of ductal tissue, consultation should be considered.
Bartholin’s Gland Abscesses
Bartholin’s glands, located in the posterior portion of the vestibule of the vagina, can form cysts from ductal occlusion. These cysts can go on to form abscesses. In addition to the abscess, the labium usually is inflamed and tender. Studies have cultured a wide range of organisms from these abscesses. These include Neisseria, Chlamydia, gram positives, gram negatives, and anaerobes. The most recent study, however, did not show any primary sexually transmitted disease (STD) organisms. Despite that fact, it is still considered necessary to culture the cervix for those organisms or to treat for them empirically.
Pilonidal Abscesses
A common abscess presenting to EDs can arise from the sacrococcygeal pilonidal sinus in the midline of the superior buttock divide at the base of the coccyx. Patients often present with painful induration of the buttock crease. Fluctuance may not be appreciated; needle aspiration or ultrasound is sometimes necessary to diagnose purulence. Cultures reveal gram-negative enteric organisms and anaerobes. These abscesses often recur unless the sinuses are excised after initial drainage.
Buttock and Perianal Abscesses
Buttock abscesses are common but must be clinically distinguished from perianal and perirectal infections ( Fig. 18-1 ). Buttock abscesses occur cutaneously and do not involve the anus. They can be incised and drained by an emergency caregiver. Perianal abscesses arise from anal crypts and impinge on the anal sphincter. A consultant surgeon is usually involved in the care of these patients. In contrast to patients with buttock abscesses, rectal examination is painful for patients with perianal abscesses. Perianal abscesses often are associated with fistula in ano. The presence of a perianal abscess also might point to other serious, related abscesses and infections of the ischiorectal, intersphincteric, and pelvirectal areas. Patients with these deeper abscesses complain of deep rectal or pelvic pain. They often have fever and appear toxic, as manifested by diaphoresis and tachycardia. A rectal examination reveals marked tenderness of the anal sphincter and rectum. Masses can be palpated with the examining finger. This condition requires urgent intervention by a consultant in an operative setting. Until recently, the predominant organisms cultured from perirectal abscesses were gram negatives and anaerobes with some gram positives. Common organisms include Escherichia coli , Bacteroides, and Streptococcus species. Recently, CA-MRSA has been cultured in up to 20% of cases.
