What is the workup and management of a rectal abscess?

From the Guidelines

The management of a rectal abscess requires prompt surgical drainage as the primary treatment. When a patient presents with symptoms such as severe rectal pain, swelling, fever, or purulent discharge, the diagnosis should be confirmed through physical examination including digital rectal exam, as suggested by the WSES-AAST guidelines 1.

Workup

The workup for a rectal abscess includes:

• A focused medical history
• A complete physical examination, including a digital rectal examination, to identify signs of sepsis, systemic infection, or other complications 1
• Laboratory tests, such as complete blood count, serum creatinine, and inflammatory markers, to assess the severity of the infection and the patient's overall condition 1
• Imaging studies, such as MRI or CT scan, may be used in cases of atypical presentation or suspicion of complex anal fistula or perianal Crohn's disease 1

Management

Surgical incision and drainage should be performed as soon as possible, typically under local anesthesia for simple perianal abscesses or regional/general anesthesia for deeper abscesses. The procedure involves:

• Making an incision over the fluctuant area
• Evacuating all purulent material
• Breaking down loculations
• Leaving the wound open to heal by secondary intention Antibiotics are not routinely required for uncomplicated abscesses after adequate drainage but should be considered for patients with systemic symptoms, immunocompromise, extensive cellulitis, or significant comorbidities, as suggested by the WSES-AAST guidelines 1. When indicated, empiric antibiotic coverage should target mixed aerobic and anaerobic flora with options including amoxicillin-clavulanate 875/125 mg orally twice daily for 5-7 days, or trimethoprim-sulfamethoxazole 1-2 DS tablets twice daily plus metronidazole 500 mg orally three times daily for 5-7 days. Post-procedure care includes:
• Sitz baths 2-3 times daily
• Regular dressing changes
• Adequate pain control with acetaminophen or NSAIDs
• Fiber supplementation to avoid constipation Patients should be informed that approximately 30-50% of anorectal abscesses may develop into fistulas requiring additional treatment. Follow-up should be arranged within 1-2 weeks to assess healing and evaluate for fistula formation. Rectal abscesses require drainage because the enclosed purulent material causes tissue destruction through pressure necrosis and bacterial enzymes, and antibiotics alone cannot adequately penetrate the abscess cavity. In patients with anorectal abscess and concomitant fistula, fistulotomy at the time of abscess drainage is only recommended for low fistulas not involving sphincter muscle, while a loose draining seton should be placed for fistulas involving any sphincter muscle 1.

From the Research

Workup of Rectal Abscess

• The workup of a rectal abscess typically involves a physical examination and a review of the patient's medical history 2, 3.
• Diagnostic tests such as ultrasound, CT scans, or MRI may be used to confirm the diagnosis and determine the extent of the abscess 3.
• Laboratory tests such as blood work and stool samples may be ordered to check for signs of infection or other underlying conditions 2, 4.

Management of Rectal Abscess

• The primary treatment for a rectal abscess is incision and drainage, which involves surgically draining the abscess to relieve symptoms and prevent further complications 2, 3, 4.
• Antibiotics may be prescribed to help prevent infection and promote healing, although their use is controversial and may depend on the individual case 2, 5.
• In some cases, a fistula may form after the abscess has been drained, which may require additional treatment such as fistulotomy or other surgical procedures 3, 4, 6.
• The management of rectal abscesses and fistulas requires a tailored approach, taking into account the individual patient's needs and the complexity of the condition 3, 4.

Factors Influencing Outcome

• The incidence of fistula formation after drainage of a rectal abscess can be influenced by factors such as the location and size of the abscess, the presence of underlying medical conditions, and the use of antibiotics 2, 5, 6.
• The risk of recurrence and complications can be minimized with proper treatment and follow-up care 3, 4.
• The use of adjuvant antibiotics after incision and drainage of anorectal abscesses may help reduce the incidence of fistula formation, although further research is needed to confirm this 2, 5.