What is the management of a grade 2 perianal fistula with an intersphincteric abscess?

Management of Grade 2 Perianal Fistula with Intersphincteric Abscess

The management of a grade 2 perianal fistula with intersphincteric abscess requires prompt surgical drainage of the abscess followed by placement of a loose draining seton for the fistula tract. 1

Initial Assessment and Diagnosis

• MRI is considered the initial procedure of choice for assessment of perianal fistulising disease, with endoanal ultrasound (EUS) as a good alternative if rectal stenosis is excluded 1
• Examination under anesthesia (EUA) is the gold standard for assessment in the hands of an experienced surgeon 1
• Proctosigmoidoscopy should be performed to evaluate for concomitant rectal inflammation, which has prognostic and therapeutic relevance 1

Primary Management of Intersphincteric Abscess

• Surgical drainage is the definitive treatment for the intersphincteric abscess and should be performed promptly after diagnosis 1, 2
• The timing of surgery should be based on the presence and severity of sepsis, with more urgent intervention required for patients with systemic signs of infection 2
• During surgical drainage, careful assessment for the presence of a fistula tract should be performed 3

Management of the Fistula Component

• For a grade 2 perianal fistula involving the sphincter muscle, a loose draining seton should be placed at the time of abscess drainage 1
• Fistulotomy should NOT be performed at the time of abscess drainage if the fistula involves any sphincter muscle, as this increases the risk of incontinence 1
• Fistulotomy may only be considered if the fistula is subcutaneous and does not involve any sphincter muscle 1

Antibiotic Therapy

• Antibiotics should be administered in the presence of:
  • Systemic signs of infection/sepsis
  • Surrounding soft tissue infection
  • Immunocompromised state 1, 2
• When indicated, empiric broad-spectrum antibiotics covering Gram-positive, Gram-negative, and anaerobic bacteria should be used 1, 2
• Metronidazole 400 mg three times daily and/or ciprofloxacin 500 mg twice daily are appropriate first-line treatments for perianal fistulae 1

Post-Drainage Management

• After initial drainage and seton placement, medical therapy should be initiated to control disease-related inflammation and increase the likelihood of tract healing 1
• For patients with Crohn's disease-related perianal fistula:
  • Thiopurines (azathioprine 1.5-2.5 mg/kg/day or mercaptopurine 0.75-1.5 mg/kg/day) are potentially effective for maintenance 1
  • Anti-TNF therapy (infliximab or adalimumab) should be reserved for patients whose fistulae are refractory to other treatments 1

Follow-up and Definitive Fistula Treatment

• Clinical assessment of decreased drainage is usually sufficient to evaluate response to treatment 1
• MRI or anal endosonography in combination with clinical assessment is recommended to evaluate improvement of fistula track inflammation 1
• Definitive fistula treatment should be delayed until the acute inflammation has resolved 3
• Options for definitive treatment include:
  • Fistulotomy (for simple fistulas not involving significant sphincter muscle)
  • Advancement flap
  • Ligation of intersphincteric fistula tract (LIFT)
  • Fibrin glue
  • Fistula plug 1, 4

Common Pitfalls to Avoid

• Relying solely on antibiotics without surgical drainage may lead to progression of infection 2
• Performing fistulotomy at the time of abscess drainage when the fistula involves sphincter muscle increases the risk of incontinence 1
• Delaying surgical intervention while attempting medical management may worsen outcomes 2
• Probing to search for a fistula during abscess drainage can cause iatrogenic complications 1