Residency · Residency · Family Medicine
Incision and Drainage of Skin Abscesses
Introduction
Skin abscesses are localized collections of pus within the dermis and subcutaneous tissue, most commonly caused by Staphylococcus aureus, including methicillin-resistant strains (MRSA). Incision and drainage (I&D) is the primary treatment and one of the most frequently performed procedures in family medicine and emergency settings.
Pathophysiology and Microbiology
Abscesses form when bacteria invade the skin through hair follicles, minor trauma, or injection sites. The body walls off the infection, creating a fluctuant collection of pus, necrotic tissue, and inflammatory cells. Community-associated MRSA (CA-MRSA) is the most common cause of skin abscesses in the United States. Other causative organisms include methicillin-sensitive S. aureus, streptococci, anaerobes, and polymicrobial flora, the last being particularly common in perianal abscesses.
Clinical Assessment
History
The assessment should establish the duration of symptoms, rate of growth, and pain severity. Prior abscesses should be inquired about, as recurrence is common, especially with MRSA colonization. Risk factors include diabetes, immunosuppression, obesity, injection drug use, and crowded living conditions. Any history of MRSA colonization or prior positive wound cultures is relevant.
Physical Examination
Fluctuance is the hallmark finding indicating a drainable collection. Erythema, warmth, tenderness, and swelling are typically present. The examiner should assess for surrounding cellulitis extending beyond the abscess margins and evaluate for signs of systemic infection including fever, tachycardia, and lymphangitis.
When to Image
Point-of-care ultrasound is highly valuable for confirming the presence of a drainable fluid collection. Ultrasound differentiates abscess, which appears as an anechoic or hypoechoic collection, from cellulitis without drainable fluid. The sensitivity of ultrasound for abscess detection is approximately 96%, compared to 83% for clinical examination alone. Imaging should be considered for deep, poorly localized, or perianal abscesses.
Incision and Drainage Technique
Preparation
Informed consent should be obtained, covering the procedure, alternatives, risks, and expected recovery. The patient is positioned for optimal access and comfort. Supplies include antiseptic, local anesthetic, a number 11 or 15 scalpel blade, hemostats, packing material, and gauze.
Anesthesia
Local infiltration with 1% lidocaine with epinephrine is performed around the abscess periphery as a field block. The anesthetic is injected into the surrounding tissue rather than directly into the abscess cavity, as injection into the cavity is painful and ineffective. Buffering lidocaine with sodium bicarbonate in a 9:1 ratio reduces injection pain. Procedural sedation may be necessary for large, painful, or pediatric cases.
Procedure Steps
The skin is cleansed with antiseptic such as chlorhexidine or povidone-iodine. The incision is made along the full length of the fluctuant area, following skin tension lines when possible. The incision must be extended sufficiently to allow complete drainage, as inadequate incision length is the most common cause of recurrence. After expressing pus, hemostats are used to break up loculations within the cavity. The cavity is irrigated with normal saline and then loosely packed with iodoform or plain gauze packing strip to prevent premature closure. A sterile dressing is applied.
Post-Procedure Care
A wound check with packing removal or change should occur in 24 to 48 hours. Patients are instructed on warm compresses and wound hygiene. Pain management with NSAIDs and acetaminophen is usually sufficient. Most wounds heal by secondary intention over 1 to 3 weeks.
Role of Antibiotics
When Antibiotics Are NOT Needed
Antibiotics are not needed for uncomplicated abscesses that are adequately drained with no surrounding cellulitis or systemic symptoms. I&D alone is curative in the majority of simple abscesses, and routine antibiotics after I&D of simple abscesses do not improve cure rates in most studies.
When to Add Antibiotics
Antibiotics should be added when there is surrounding cellulitis extending beyond the abscess margin, systemic signs of infection such as fever or tachycardia, immunocompromise, an abscess in a high-risk location (face, hand, genitalia, or perianal area), multiple or recurrent abscesses, or failed initial I&D.
Antibiotic Selection
Empiric therapy should target MRSA, with trimethoprim-sulfamethoxazole (TMP-SMX DS twice daily) or doxycycline 100 mg twice daily as first-line options. The typical duration is 5 to 7 days for uncomplicated cases. A wound culture should be obtained to guide therapy when antibiotics are prescribed or when treatment fails. Clindamycin is an alternative, though increasing resistance rates limit its utility.
Complications and Recurrence
Recurrence occurs in approximately 20 to 50% of patients and is associated with MRSA colonization and ongoing risk factors. Decolonization protocols for recurrent abscesses include mupirocin nasal ointment, chlorhexidine body washes, and laundering personal items. Complications of I&D include bleeding, damage to underlying structures, incomplete drainage, and scarring. Surgical referral should be considered for perianal abscesses with possible fistula, pilonidal abscesses, and large or deep abscesses.
Key Clinical Pearls
Incision and drainage is the definitive treatment for skin abscesses; antibiotics alone without drainage are insufficient. Point-of-care ultrasound should be used to confirm the presence of a drainable collection, especially when fluctuance is uncertain. The incision must be long enough to allow complete drainage and loculation breakdown, as insufficient incision length is the most common cause of treatment failure. Antibiotics should be reserved for patients with surrounding cellulitis, systemic symptoms, immunocompromise, or high-risk abscess locations.
References
- Stevens DL, et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the IDSA. Clin Infect Dis. 2014;59(2):e10-e52.
- Talan DA, et al. Trimethoprim-sulfamethoxazole versus placebo for uncomplicated skin abscess. N Engl J Med. 2016;374(9):823-832.
- Squire BT, et al. ABSCESS: applied bedside sonography for convenient evaluation of superficial soft tissue infections. Acad Emerg Med. 2005;12(7):601-606.
- Singer AJ, Talan DA. Management of skin abscesses in the era of MRSA. N Engl J Med. 2014;370(11):1039-1047.