What is the treatment for a rectal abscess?

Treatment of Rectal Abscess

Surgical incision and drainage is the definitive treatment for all rectal abscesses and should be performed urgently, with timing based on the presence and severity of sepsis. 1, 2

Diagnosis and Initial Assessment

Before proceeding to drainage, perform the following evaluation:

• Digital rectal examination is essential to diagnose the abscess and assess its location 1
• Screen for diabetes mellitus by measuring serum glucose, hemoglobin A1c, and urine ketones, as diabetes is a common comorbidity in these patients 1
• For patients with systemic infection or sepsis, obtain complete blood count, serum creatinine, and inflammatory markers (C-reactive protein, procalcitonin) 1

When to Order Imaging

• Imaging is not routinely required for straightforward perianal abscesses 1, 3
• Consider MRI, CT scan, or endosonography in cases of atypical presentation, suspected occult supralevator abscesses, or suspected perianal Crohn's disease 1, 3

Surgical Management

Timing and Setting

• Patients with sepsis, immunosuppression, diabetes, or diffuse cellulitis require emergent drainage 2
• Fit, immunocompetent patients with small perianal abscesses without systemic signs can be managed in an outpatient setting with bedside drainage in the emergency department 2, 3, 4
• Deeper or more complex abscesses may require drainage in the operating room 1

Surgical Technique

• Keep the incision as close as possible to the anal verge to minimize the length of a potential fistula while ensuring adequate drainage 2, 3
• For larger abscesses, use multiple counter incisions rather than a single long incision to prevent delayed wound healing 3
• Examine for an associated fistula tract during the procedure 3

Management of Associated Fistulas

• If a low subcutaneous fistula not involving sphincter muscle is identified, perform fistulotomy at the time of abscess drainage 1, 3
• For fistulas involving sphincter muscle, place a loose draining seton rather than performing immediate fistulotomy to prevent incontinence 1, 2, 3
• Avoid probing to search for a fistula if one is not obvious, as this may cause iatrogenic complications 1

Antibiotic Therapy

When Antibiotics Are NOT Needed

• Antibiotics are not routinely indicated after adequate surgical drainage in immunocompetent patients 1, 3

When Antibiotics ARE Indicated

Administer antibiotics in the following situations:

• Presence of sepsis or systemic signs of infection 1, 3
• Immunocompromised patients 1, 3
• Incomplete source control 3
• Significant surrounding cellulitis 3

Antibiotic Selection

• When indicated, use empiric broad-spectrum antibiotic therapy covering Gram-positive, Gram-negative, and anaerobic bacteria 1, 3
• Consider sampling drained pus in high-risk patients or those with risk factors for multidrug-resistant organisms 1
• Inadequate antibiotic coverage after drainage of complicated abscesses results in a six-fold increase in readmission rate for recurrence 5

Post-Procedure Care and Follow-Up

• Close follow-up is essential to monitor for recurrence or fistula development 3
• The recurrence rate after drainage can be as high as 44%, with risk factors including inadequate drainage, loculations, horseshoe-type abscess, and delayed time from disease onset to incision 2, 3
• No definitive recommendation can be made regarding wound packing after drainage based on current evidence 1
• Routine imaging after incision and drainage is usually not required unless there is recurrence, suspected inflammatory bowel disease, or evidence of a fistula/non-healing wound 3

Critical Pitfalls to Avoid

• Delaying drainage in patients with sepsis or diabetes can lead to necrotizing soft-tissue infection with mortality rates up to 40% 6
• Performing immediate fistulotomy on fistulas involving sphincter muscle risks fecal incontinence 1, 2
• Inadequate drainage or single long incisions increase recurrence risk 2, 3