What is the most appropriate next step in management for a 24-year-old male with a tender, fluctuating perianal mass and a fistula, recurrent spontaneous drainage, and a normal abdominal examination?

Management of Recurrent Perianal Abscess with Fistula

This patient requires examination under general anesthesia (EUA) with immediate incision and drainage, fistula assessment, and seton placement if the fistula involves sphincter muscle. 1, 2

Rationale for Examination Under Anesthesia

The presence of a visible fistula with a fluctuating mass and history of recurrent spontaneous drainage mandates EUA as the procedure of choice. 1, 2 This approach allows:

• Immediate therapeutic intervention including abscess drainage and seton placement in a single session 1
• Complete assessment of fistula anatomy that cannot be adequately performed at bedside due to pain and anatomical distortion from acute infection 1, 2
• Identification of occult collections that may be present in approximately one-third of perianal abscess cases 1, 2

Why Other Options Are Inadequate

CT Pelvis (Option A)

• Imaging should not delay surgical drainage when a perianal abscess is clinically evident 1, 2
• Clinical examination identifies >94% of perirectal abscesses; imaging is reserved only for atypical presentations or suspected supralevator/intersphincteric abscesses 2
• This patient has clear clinical findings (fluctuant mass, visible fistula) that do not require imaging confirmation 1, 2

Oral Antibiotics with Outpatient Follow-up (Option B)

• Antibiotics alone are never sufficient for abscess management—incision and drainage is mandatory for every perianal abscess 2, 3
• An undrained abscess can expand into adjacent spaces and progress to systemic infection 2
• Antibiotics are only adjunctive therapy indicated for sepsis, extensive cellulitis, or immunosuppression—not as primary treatment 1, 2

Bedside Needle Aspiration (Option C)

• Needle aspiration has a 41% recurrence rate compared to 15% with proper incision and drainage 2, 4
• This patient's recurrent presentations with spontaneous drainage indicate inadequate source control, which needle aspiration will not address 2, 3
• Complete drainage with breaking up of loculations is essential, as inadequate drainage is the principal cause of recurrence (up to 44% recurrence rate) 2, 3, 4

Specific Management During EUA

Abscess Drainage

• Perform incision as close as possible to the anal verge to minimize potential fistula tract length while ensuring complete drainage 1, 2, 4
• Thoroughly evacuate all pus and break up any loculations, as loculations are a specific risk factor for recurrence 2, 3
• Use multiple counter-incisions for large abscesses rather than a single long incision to avoid step-off deformity and delayed healing 2

Fistula Management

• If the fistula is low-lying and does not involve sphincter muscle (subcutaneous), perform immediate fistulotomy 1, 2, 3
• If the fistula involves any portion of the sphincter muscle, place a loose draining seton only—definitive fistula repair must be deferred to avoid incontinence risk 1, 2, 3
• Do NOT probe for additional fistulas if none are obvious, as probing causes iatrogenic injury without reducing recurrence 1, 2, 3

Critical Pitfall to Avoid

The recurrent nature of this patient's presentations strongly suggests an underlying fistula tract that was not adequately addressed previously. 3 Approximately one-third of perianal abscesses have an associated fistula-in-ano, which dramatically increases recurrence risk 1, 2, 3. Simple drainage without fistula management results in 44% recurrence compared to 21% when fistula is addressed 5.

Post-Operative Considerations

Antibiotic Therapy

• Routine antibiotics are NOT required after adequate surgical drainage 1, 2
• Administer antibiotics only if: sepsis/systemic signs present, extensive surrounding cellulitis, immunocompromised state, or incomplete source control 1, 2, 3
• If antibiotics are indicated, use empiric broad-spectrum coverage (Gram-positive including MRSA, Gram-negative, and anaerobes) as these infections are polymicrobial 2, 3

Follow-Up Imaging

• For recurrent abscesses specifically, follow-up imaging is recommended to assess for persistent fistula tracts or non-healing wounds 3, 4
• MRI is the gold standard with 76-100% accuracy if Crohn's disease is suspected 1, 2, 3

Screen for Underlying Disease

• Rule out Crohn's disease in patients with recurrent perianal abscesses, as approximately one-third of Crohn's patients develop anorectal abscesses 1, 3
• Screen for diabetes mellitus by checking serum glucose and hemoglobin A1c 2, 3