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Cutaneous Abscess

By A. Damian Dhar, MD, JD, Private Practice, North Atlanta Dermatology

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Patient Education

A cutaneous abscess is a localized collection of pus in the skin and may occur on any skin surface. Symptoms and signs are pain and a tender and firm or fluctuant swelling. Diagnosis is usually obvious by examination. Treatment is incision and drainage.

Risk factors for cutaneous abscesses include the following:

  • Bacterial overgrowth

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

  • Immunosuppression

  • Impaired circulation

Bacteria causing cutaneous abscesses are typically indigenous to the skin of the involved area. For abscesses on the trunk, extremities, axillae, or head and neck, the most common organisms are Staphylococcus aureus (with methicillin-resistant S. aureus [MRSA] being the most common in the US) and streptococci.

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). Carbuncles and furuncles are types of cutaneous abscesses.

Symptoms and Signs

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. The abscess may then spontaneously drain. Local cellulitis, lymphangitis, regional lymphadenopathy, fever, and leukocytosis are variable accompanying features.

Diagnosis

  • Examination

  • Culture to identify MRSA

Diagnosis is usually obvious by examination. Culture is recommended, primarily to identify MRSA.

Conditions resembling simple cutaneous abscesses include hidradenitis suppurativa and ruptured epidermal cysts. Epidermal cysts (often incorrectly referred to as sebaceous cysts) rarely become infected; however, rupture releases keratin into the dermis, causing an exuberant inflammatory reaction sometimes clinically resembling infection. Culture of these ruptured cysts seldom reveals any pathogens. Perineal abscesses may represent cutaneous emergence of a deeper perirectal abscess or drainage resulting from Crohn disease via a fistulous tract. These other conditions are usually recognizable by history and rectal examination.

Treatment

  • Incision and drainage

  • Sometimes antibiotics

Some small abscesses resolve without treatment, coming to a point and draining. Warm compresses help accelerate the process. Incision and drainage are 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 h later. However, recent data have not proven the effectiveness of routine irrigation or packing (1,2). Local heat and elevation may hasten resolution of inflammation.

Antibiotics have traditionally been considered unnecessary (3) 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 drug active against MRSA (eg, trimethoprim/sulfamethoxazole, clindamycin; for severe infection, vancomycin) pending results of bacterial culture. However, recent studies have suggested marginally better results when antibiotics are added to usual treatment of even uncomplicated abscesses (3).

Treatment references

  • Chinnock B, Hendey GW: Irrigation of cutaneous abscesses does not improve treatment success. Ann Emerg Med 67(3):379-383, 2016. doi: 10.1016/j.annemergmed.2015.08.007.

  • O'Malley GF, Dominici P, Giraldo P, et al: Routine packing of simple cutaneous abscesses is painful and probably unnecessary. Acad Emerg Med 16(5):470-473, 2009. doi: 10.1111/j.1553-2712.2009.00409.x.

  • Trimethoprim-sulfamethoxazole versus placebo for uncomplicated skin abscess. N Engl J Med 374(9):823-832, 2016. doi: 10.1056/NEJMoa1507476.

Key Points

  • Pathogens reflect flora of the involved area (eg, S. aureus and streptococci in the trunk, axilla, head, and neck), but MRSA has become more common.

  • Culture abscesses to identify MRSA.

  • Drain abscesses accompanied by significant pain, tenderness, and swelling and provide adequate analgesia and, when indicated, sedation.

  • Avoid antibiotics in simple abscesses.