What is the treatment for a patient presenting with symptoms of a peri-anal abscess?

Treatment of Perianal Abscess

Immediate incision and drainage is the definitive treatment for all perianal abscesses, and should be performed within 24 hours for uncomplicated cases or emergently for patients with sepsis, immunosuppression, diabetes, or diffuse cellulitis. 1, 2

Clinical Presentation and Diagnosis

Typical symptoms include:

• Perianal pain, swelling, and fever 3
• Discharge of pus may be present 3
• Deeper abscesses may present with pain referred to the perineum, low back, and buttocks 3
• Urinary retention can occur 3
• Critical caveat: Symptoms are frequently absent or diminished in elderly, debilitated, diabetic, or immunosuppressed patients—maintain high clinical suspicion in these populations 3

Diagnostic approach:

• History and physical examination, including digital rectal examination, are usually sufficient for small and superficial abscesses 3
• Check for undiagnosed Crohn's disease, especially in recurrent cases—inspect for surgical scars, anorectal deformities, and signs of perianal Crohn's disease 3
• Deeper abscesses reveal a tender, indurated area above the anorectal ring on rectal examination 3

Imaging is NOT routinely needed but consider in:

• Atypical presentations (lower back pain, severe anal pain without fissure, urinary retention) 3
• Suspected supralevator or intersphincteric abscess 3, 1
• Suspicion of perianal Crohn's disease or complex fistula 3
• CT scan offers the best balance of availability and speed in emergency settings 3

Laboratory Testing

Obtain labs only when clinically indicated:

• For suspected systemic infection or sepsis: complete blood count, serum creatinine, inflammatory markers (CRP, procalcitonin, lactate) 3
• Check serum glucose, hemoglobin A1c, and urine ketones to screen for undetected diabetes 4

Surgical Management

Incision and drainage technique:

• Keep the incision as close as possible to the anal verge to minimize potential fistula length while ensuring adequate drainage 1, 2
• For larger abscesses, use multiple counter incisions rather than a single long incision to prevent step-off deformity and delayed healing 1
• Complete drainage is essential—inadequate drainage is associated with high recurrence rates (up to 44%) 1, 2

Location-specific approach:

• Perianal and ischioanal abscesses: drain via overlying skin 1
• Intersphincteric abscesses: drain via rectal lumen 1
• Supralevator abscesses: drain via rectal lumen or externally via skin 1

Timing of surgery:

• Emergency drainage: sepsis, severe sepsis, septic shock, immunosuppression, diabetes mellitus, or diffuse cellulitis 1
• Within 24 hours: all other cases 1
• Bedside drainage in the emergency department is safe and effective for small, uncomplicated abscesses in immunocompetent patients without fever 5

Management of Concomitant Fistulas

If a fistula is identified during drainage:

• Perform fistulotomy ONLY for low fistulas not involving sphincter muscle 1, 2, 4
• Place a loose draining seton for any fistula involving sphincter muscle to prevent incontinence 1, 2, 4
• Do NOT actively probe to search for a fistula if one is not obvious—this may cause iatrogenic complications 3, 4

Evidence note: A 2010 Cochrane review showed that treating low fistulas at the time of abscess drainage significantly reduces recurrence (RR=0.13) without statistically significant incontinence at one year, but this should only be done in carefully selected patients 6

Antibiotic Therapy

Antibiotics are NOT routinely indicated after adequate surgical drainage in immunocompetent patients. 1, 2, 4

Use antibiotics ONLY when:

• Sepsis or systemic signs of infection present 1, 2, 4
• Immunocompromised patients 1, 2, 4
• Incomplete source control or significant surrounding cellulitis 1, 2
• Diabetes mellitus or other immunosuppression 1

When indicated, use empiric broad-spectrum coverage:

• Cover Gram-positive, Gram-negative, and anaerobic bacteria (abscesses are frequently polymicrobial) 1, 2
• Consider sampling drained pus in high-risk patients or those with risk factors for multidrug-resistant organisms 4

Post-Operative Care

Wound management:

• The role of wound packing remains controversial—some evidence suggests it may be costly and painful without adding benefit 1, 4
• No definitive recommendation can be made based on current evidence 4

Follow-Up and Recurrence Prevention

Routine imaging after drainage is NOT required unless: 1, 2

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

Risk factors for recurrence include:

• Inadequate drainage 1, 2
• Loculations (recurrence rate up to 44%) 1
• Horseshoe-type abscess 1
• Delayed time from disease onset to incision 1, 2
• Fever and larger abscess size at initial presentation are risk factors for late fistula formation 5

Special Considerations for Crohn's Disease

In patients with known or suspected Crohn's disease:

• Perform adequate surgical drainage without searching for an associated fistula 3
• Assess the rectum at time of abscess drainage to evaluate for signs of proctitis 3
• Proctitis is a predictive factor for persistent non-healed fistula tracts and higher proctectomy rates 1
• Do NOT lay open any fistula—place a loose draining seton if an obvious fistula exists 3
• No additional surgical fistula treatment modality should be performed in the emergency setting 3