Cutaneous Abscess

Risk factors for cutaneous abscesses include the following:

• Skin barrier disruption

• Injection drug use

• Bacterial overgrowth

• Antecedent trauma (particularly when a foreign body is present)

• Immunosuppression

• Impaired circulation

Bacteria causing cutaneous abscesses are typically commensal or colonizing organisms originating from the skin of the involved area or from adjacent mucous membranes. S. aureus (including MRSA) and streptococci continue to be common causes of abscesses on the trunk, extremities, axillae, and head and neck; these can also be polymicrobial.

Abscesses in the perineal (ie, inguinal, vaginal, buttock, perirectal) region contain organisms found in the stool, commonly anaerobes or a combination of aerobes and anaerobes (see table Classification of Common Pathogenic Bacteria).

Cutaneous abscesses are painful, tender, indurated, and usually erythematous.

They vary in size, typically 1 to 3 cm in length, but are sometimes much larger. Initially the swelling is firm; later, as the abscess points, the overlying skin becomes thin and feels fluctuant. Fluctuance is a key feature when present; however, in very deep abscesses, fluctuance may be obscured by overlying soft tissue. The abscess may then spontaneously drain.

Local cellulitis, lymphangitis, regional lymphadenopathy, fever, and leukocytosis are variable accompanying features.

• Primarily history and physical examination

• Culture to identify MRSA

The diagnosis of cutaneous abscess is usually based on clinical evaluation. Supportive clinical findings of a cutaneous abscess include a suggestive history and painful, tender, and fluctuant erythematous swelling on examination.

Gram stain and culture are generally recommended, primarily to identify MRSA and obtain antimicrobial susceptibility testing (1). Although ruptured epidermal cysts mimic abscesses and are often cultured, they rarely reveal pathogens because the inflammation is typically a foreign body reaction to keratin rather than a true bacterial infection.

Point-of-care ultrasound can improve diagnostic accuracy and help distinguish an abscess from cellulitis when there is diagnostic uncertainty (2).

• Incision and drainage

• Sometimes antibiotics

The treatment of cutaneous abscesses generally depends on lesion size and associated clinical features such as pain and swelling (1). Some small abscesses resolve without treatment, coming to a point and draining. Warm compresses help accelerate the process. Incision and drainage is indicated when significant pain, tenderness, and swelling are present; it is unnecessary to await fluctuance. Under sterile conditions, local anesthesia is given as either a lidocaine injection or a freezing spray.). Some small abscesses resolve without treatment, coming to a point and draining. Warm compresses help accelerate the process. Incision and drainage is indicated when significant pain, tenderness, and swelling are present; it is unnecessary to await fluctuance. Under sterile conditions, local anesthesia is given as either a lidocaine injection or a freezing spray.

Patients with large, extremely painful abscesses may benefit from IV sedation and analgesia during drainage. A single puncture with the tip of a scalpel is often sufficient to open the abscess. After the pus drains, the cavity should be bluntly probed with a gloved finger or curette to clear loculations. Irrigation with normal saline is optional. Packing the cavity loosely with a gauze wick reduces the dead space and prevents formation of a seroma. The wick is typically removed 24 to 48 hours later. However, data suggest that routine irrigation or packing for abscesses < 5 cm in diameter is unnecessary (2, 3). Local heat and elevation may hasten resolution of inflammation.

Antibiotics have traditionally been considered unnecessary unless the patient has signs of systemic infection, cellulitis, multiple abscesses, immunocompromise, or a facial abscess in the area drained by the cavernous sinus. In these cases, empiric therapy should be started with a medication active against MRSA (eg, sulfamethoxazole/trimethoprim, clindamycin; for severe infection, vancomycin) pending results of bacterial culture. However, subsequent studies have suggested lower rates of treatment failure and recurrence when antibiotics are added for any abscess that requires treatment in locations where MRSA is prevalent ((eg, sulfamethoxazole/trimethoprim, clindamycin; for severe infection, vancomycin) pending results of bacterial culture. However, subsequent studies have suggested lower rates of treatment failure and recurrence when antibiotics are added for any abscess that requires treatment in locations where MRSA is prevalent (4).