What is the best course of treatment for a patient with a localized skin infection, likely cellulitis, presenting with a 2 cm abscess, purulent drainage, and a 2 cm undermining pocket on their right upper back, who has been using hydrogen peroxide and has no other areas of concern?

Management of Localized Skin Abscess with Undermining and Purulent Drainage

This patient requires urgent care referral for formal incision and drainage with adjunctive oral antibiotics, as the presence of a 2 cm undermining pocket with purulent drainage and surrounding cellulitis classifies this as a complex abscess that cannot be adequately managed with simple drainage alone. 1

Classification: Complex vs. Simple Abscess

This case represents a complex abscess rather than a simple one based on several key features: 2

• Undermining pocket (2 cm) indicates extension beyond simple borders 1
• Necrotic tissue suggests deeper tissue involvement 1
• Surrounding cellulitis (warmth, erythema, induration) extends beyond the abscess borders 1
• Simple abscesses have induration and erythema limited only to the defined abscess area without extension 1

Treatment Algorithm

Immediate Surgical Management Required

Formal incision and drainage is mandatory and should be performed at urgent care or emergency department: 1, 2

• The undermining pocket requires proper exploration and debridement of necrotic tissue 1
• Multiple counter incisions may be needed rather than a single long incision to prevent step-off deformity and delayed healing 2
• Simple dabbing and cleaning in the field is insufficient for complex abscesses 1

Adjunctive Antibiotic Therapy is Indicated

Unlike simple abscesses where drainage alone suffices, this patient requires systemic antibiotics because: 1, 2

• Significant cellulitis surrounds the abscess 1
• Necrotic tissue and undermining suggest incomplete source control with field drainage alone 1

Empiric antibiotic coverage should target:

• MRSA coverage is essential given the purulent nature and community-acquired setting 1
• Oral options include clindamycin or trimethoprim-sulfamethoxazole (TMP-SMX) 3
• Both agents showed 81-83% cure rates in abscesses with incision and drainage, significantly better than drainage alone (69%) 3
• Clindamycin may reduce recurrence rates (6.8% vs 13.5% with TMP-SMX) but has higher adverse event rates (21.9% vs 11.1%) 3

Duration: 5-10 days depending on severity and clinical response 1, 4

Critical Management Points

What Was Done Correctly

• Discontinuing hydrogen peroxide was appropriate, as it damages infected tissue 1
• Normal saline irrigation is the correct approach 1
• Recognizing the need for urgent care referral 1

Common Pitfalls to Avoid

Do not treat this as a simple abscess: 1, 2

• Simple abscesses can be drained without antibiotics, but this classification does not apply here 1
• The undermining pocket and surrounding cellulitis mandate both proper surgical drainage and antibiotics 1

Inadequate drainage leads to treatment failure: 2

• Field drainage with "gentle pressure and dabbing" is insufficient for undermining pockets 1
• Proper exploration and debridement of necrotic tissue requires surgical intervention 1, 2

Culture should be obtained: 1

• Abscess drainage should be cultured to guide antibiotic therapy if initial treatment fails 1
• This is particularly important given rising MRSA prevalence (49.4% in community abscesses) 3

Disposition and Follow-up

Urgent care or ED referral is mandatory for: 1

• Proper incision and drainage with exploration of undermining pocket 1, 2
• Initiation of appropriate oral antibiotics 1
• Culture of purulent material 1

Outpatient management is appropriate if the patient has no systemic signs (fever, altered mental status, hemodynamic instability) 1

Follow-up in 48-72 hours to ensure clinical improvement, with treatment extended beyond 5 days if infection has not improved 1