What is the recommended treatment for a patient with a suspected abscess?

Management of Suspected Abscess

The cornerstone of treatment for any suspected abscess is incision and drainage (I&D), which should be performed urgently based on the presence and severity of sepsis, with antibiotics reserved only for specific high-risk situations. 1, 2

Initial Diagnostic Approach

Clinical Examination

• Perform a focused history and complete physical examination, including digital rectal examination (DRE) for suspected anorectal abscesses. 1, 3 DRE provides immediate information about presence, location, and characteristics of the abscess and can identify occult supralevator abscesses not apparent on external examination. 3

• Check serum glucose, hemoglobin A1c, and urine ketones to identify undetected diabetes mellitus, as this is a strong recommendation even with low-quality evidence. 1

• For patients with signs of systemic infection or sepsis, obtain complete blood count, serum creatinine, and inflammatory markers (C-reactive protein, procalcitonin, lactates). 1

Imaging Considerations

• Most typical abscesses can be diagnosed by clinical examination alone—imaging is NOT routinely needed. 2, 3 Ordering imaging when clinical examination is adequate delays definitive treatment. 3

• Consider imaging only for: 1, 2

  • Atypical presentations
  • Suspected occult supralevator abscesses
  • Complex anal fistula
  • Suspected perianal Crohn's disease
  • Recurrent abscesses

• When imaging is needed, CT scan offers advantages of short acquisition time and widespread availability for initial assessment, while MRI is the gold standard for complex cases with 76-100% accuracy. 2, 3

Surgical Management

Timing of Drainage

Emergency drainage (immediate) is required for: 2, 4

• Sepsis, severe sepsis, or septic shock
• Immunosuppression
• Diabetes mellitus
• Diffuse cellulitis

In the absence of these high-risk features, surgical drainage should ideally be performed within 24 hours. 2, 4

Surgical Technique

• Incision and drainage is the definitive treatment for all abscesses—this is non-negotiable. 1, 2

• Keep the incision as close as possible to the anal verge (for perianal abscesses) to minimize potential fistula length while ensuring adequate drainage. 2, 4

• Complete drainage is absolutely essential—inadequate drainage is the leading cause of recurrence with rates as high as 44%. 2, 4 Thoroughly evacuate all pus and actively probe the cavity to break up any loculations. 4

• For large abscesses, use multiple counter incisions rather than a single long incision, which creates step-off deformity and delays healing. 2, 4

Management of Concomitant Fistulas

• If an obvious fistula is found during drainage, perform fistulotomy ONLY for low fistulas not involving sphincter muscle (subcutaneous fistulas). 1, 2

• For any fistula involving sphincter muscle, place a loose draining seton to avoid incontinence risk. 1, 4

• Do NOT blindly probe or use hydrogen peroxide to search for a fistula if not obvious, as this causes iatrogenic complications. 4

Antibiotic Therapy

Antibiotics are NOT routinely indicated after adequate surgical drainage. 2 This is a critical point—drainage alone is sufficient for most cases. 5, 6

Specific Indications for Antibiotics

Consider antibiotics ONLY when: 2, 4

• Sepsis or systemic signs of infection present
• Surrounding soft tissue infection or significant cellulitis
• Immunocompromised state or disturbances of immune response
• Inadequate source control despite drainage
• Incomplete source control or abscess with significant cellulitis

Antibiotic Selection

• Use empiric broad-spectrum coverage targeting Gram-positive (including MRSA), Gram-negative, and anaerobic bacteria, as these abscesses are frequently polymicrobial. 2, 4

• Consider obtaining pus cultures in recurrent cases or high-risk patients, as MRSA prevalence can be as high as 35% in anorectal abscesses. 4

• A 5-10 day course of antibiotics following drainage may reduce fistula formation by 36% in patients with surrounding cellulitis or systemic sepsis. 4

Post-Operative Care

Wound Packing

• The role of wound packing remains controversial and cannot be strongly recommended. 1, 2 Evidence suggests packing may be costly and painful without adding benefit to healing. 2, 4

• If packing is used, it should be removed within 24 hours and changed regularly until cavity heals. 4

Follow-Up

• Routine imaging after incision and drainage is NOT required. 2

• Consider follow-up imaging in cases of: 2, 3

  • Recurrence
  • Suspected inflammatory bowel disease
  • Evidence of fistula or non-healing wound

• Re-evaluate at 7 days—persistent fever or failure to improve indicates inadequate source control requiring repeat imaging or intervention. 4

Special Populations

Small Perianal Abscesses

• In fit, immunocompetent patients with a small perianal abscess and without systemic signs of sepsis, consider outpatient management. 1

Suspected Crohn's Disease

• If perianal Crohn's disease is suspected, perform endoscopic assessment of the rectum, as proctitis predicts persistent non-healed fistula tracts and higher proctectomy rates. 2, 4

• For confirmed Crohn's disease with fistulizing disease, consider metronidazole and/or ciprofloxacin in addition to seton placement. 4

Critical Pitfalls to Avoid

• Do NOT perform simple needle aspiration for most abscesses—this has a 41% recurrence rate compared to 15% with proper incision and drainage. 4

• Do NOT delay drainage if imaging is not immediately available when an abscess is clinically suspected. 2

• Do NOT perform fistulotomy on high fistulas involving sphincter muscle at initial drainage. 1, 4

• Do NOT prescribe antibiotics routinely without specific indications—drainage is the primary therapy. 2, 5