What is the diagnosis and treatment for a skin and subcutaneous tissue abscess?

Diagnosis and Treatment of Skin and Subcutaneous Tissue Abscess

Incision and drainage (I&D) is the definitive treatment for cutaneous abscesses, and antibiotics are unnecessary for simple abscesses after adequate drainage. 1

Clinical Diagnosis

Diagnosis is primarily clinical based on physical examination findings 2:

• Local signs: Pain, swelling, erythema, and fluctuance with purulent drainage 2
• Point-of-care ultrasound (POCUS): Highly effective for differentiating abscess from cellulitis and guiding management decisions 3
• Depth assessment: Abscesses >0.4 cm deep from skin surface typically require drainage (sensitivity 85%, specificity 68%) 3

Important caveat: In morbidly obese patients or those with deep multilayer wounds, external signs may appear late but will always eventually manifest 2

Classification: Simple vs. Complex Abscess

Simple Abscess 1

• Induration and erythema limited to the defined abscess area
• No extension into deeper tissues or multiloculated spread
• Absence of systemic signs of infection

Complex Abscess 1

• Perianal/perirectal locations
• IV drug injection sites
• Significant surrounding cellulitis extending beyond abscess borders

Primary Treatment: Incision and Drainage

All infected abscesses should be opened, evacuated, and allowed to heal by secondary intention 2:

• I&D is the definitive treatment and should be performed promptly for all cutaneous abscesses 1
• Do NOT pack wounds routinely: Simply covering with dry sterile gauze is adequate, as packing causes more pain without improving healing 1, 4
• Do NOT use needle aspiration: Only 25% success rate overall and <10% with MRSA 1

Exception: Wounds larger than 5 cm may benefit from packing to reduce recurrence 5

When Antibiotics Are NOT Needed

For simple abscesses with adequate I&D, antibiotics are unnecessary 2, 1:

• Minimal surrounding cellulitis (<5 cm of erythema and induration) 2
• Temperature <38.5°C 2
• Pulse rate <100 beats/min 2
• No systemic signs of infection 1

Studies of subcutaneous abscesses found no benefit for antibiotic therapy when combined with drainage 2

When to Add Antibiotics

Add antibiotics when any of the following are present 1:

Systemic Inflammatory Response Syndrome (SIRS) criteria 1:

• Temperature >38°C or <36°C
• Tachypnea >24 breaths/min
• Tachycardia >90 beats/min
• WBC >12,000 or <4,000 cells/µL

High-risk situations 1:

• Severe or extensive disease involving multiple infection sites
• Rapid progression with associated cellulitis
• Immunocompromised patients
• Extremes of age
• Abscess in difficult-to-drain areas
• Associated septic phlebitis
• Incomplete source control
• Lack of response to I&D alone

For patients meeting antibiotic criteria: A short course of 24-48 hours may be indicated if temperature ≥38.5°C or pulse rate ≥100 beats/min 2

Antibiotic Selection for Community-Acquired MRSA

First-line oral options for outpatient empiric CA-MRSA coverage 1:

• Clindamycin: 150-450 mg every 6 hours (adults); 8-20 mg/kg/day divided into 3-4 doses (pediatrics) 6
• TMP-SMX 1
• Doxycycline or minocycline 1
• Linezolid 1

Duration: 5-10 days when antibiotics are used 1

Critical warning: Do NOT use fluoroquinolones for MRSA coverage—they are inadequate 1

Complex Abscess Management

For perianal/perirectal abscesses or IV drug user abscesses 1:

• I&D plus empiric broad-spectrum antibiotics covering Gram-positive, Gram-negative, and anaerobic bacteria 1
• Surgical drainage with identification of fistula tracts (perianal/perirectal) 1
• Evaluation for endocarditis if systemic signs persist (IV drug users) 1
• Foreign body removal and screening for HIV/HCV/HBV (IV drug users) 1

Culture Recommendations

• Gram stain and culture of pus are recommended for carbuncles and abscesses 1
• Treatment without culture is reasonable in typical cases 1
• Culture results guide antibiotic adjustment if treatment fails 1

Critical Pitfalls to Avoid

• Do NOT use rifampin as single agent or adjunctive therapy for skin abscesses 1
• Do NOT routinely prescribe antibiotics for simple abscesses after adequate I&D—this contributes to resistance without improving outcomes 2, 1
• Do NOT pack wounds routinely—evidence shows no benefit and increased pain 1, 4
• Do NOT use fluoroquinolones for MRSA coverage 1
• Do NOT use needle aspiration as primary treatment 1