Who needs antibiotics post-operatively after surgical drainage of a perianal abscess?

From the Guidelines

Antibiotics are not routinely needed after surgical drainage of a perianal abscess for most patients, but should be considered in high-risk patients, such as those with sepsis, surrounding soft tissue infection, or disturbances of the immune response, as suggested by the WSES-AAST guidelines 1. The primary treatment for perianal abscess is adequate surgical drainage, which is usually sufficient without antibiotic therapy. However, certain high-risk patients should receive antibiotics post-operatively, including those who are immunocompromised, patients with significant cellulitis extending beyond the abscess, those with systemic signs of infection, patients with prosthetic heart valves or other implants at risk for endocarditis, and those with extensive tissue involvement or recurrent abscesses.

When antibiotics are indicated, common regimens include amoxicillin-clavulanate 875/125 mg twice daily for 5-7 days, or for penicillin-allergic patients, trimethoprim-sulfamethoxazole DS twice daily plus metronidazole 500 mg three times daily for 5-7 days. The rationale for selective antibiotic use is that perianal abscesses are typically polymicrobial infections with both aerobic and anaerobic bacteria from the gastrointestinal tract, but adequate drainage alone resolves most infections by removing the purulent collection, while unnecessary antibiotics may contribute to antimicrobial resistance and side effects without improving outcomes in uncomplicated cases.

Some key points to consider when deciding on antibiotic therapy for perianal abscess include:

• The presence of sepsis or surrounding soft tissue infection, which may require antibiotic therapy 1
• The patient's immune status, with immunocompromised patients potentially requiring antibiotic therapy 1
• The presence of systemic signs of infection, such as fever or tachycardia, which may indicate the need for antibiotic therapy 1
• The presence of prosthetic heart valves or other implants at risk for endocarditis, which may require antibiotic therapy 1

It's also important to note that cultures from abscesses and other purulent SSTIs are recommended in patients treated with antibiotic therapy, patients with severe local infection or signs of systemic illness, patients who have not responded adequately to initial treatment, and if there is concern for a cluster or outbreak 1. However, the most recent and highest quality study, the WSES-AAST guidelines, suggests that antibiotics should be used selectively in high-risk patients, and that adequate drainage alone is usually sufficient for most patients 1.

From the Research

Patient Selection for Post-Operative Antibiotics

The decision to administer antibiotics post-operatively after surgical drainage of a perianal abscess depends on various factors, including the complexity of the abscess, patient demographics, and the presence of underlying medical conditions.

• Patients with complicated perianal abscesses, such as those with multiple abscesses or significant comorbidities, may benefit from post-operative antibiotics 2.
• However, for uncomplicated perianal abscesses, routine use of post-operative antibiotics may not be necessary 3.

Antibiotic Regimens

The choice of antibiotic regimen is crucial in preventing fistula formation and recurrent abscesses.

• A study found that a 7-10 day course of post-operative antibiotics, including ciprofloxacin and metronidazole, played an important role in preventing fistula formation 4.
• Another study suggested that antibiotic therapy, including amoxicillin and clavulanic acid, had no influence on anal fistula or recurrent perianal abscess formation after incision and drainage of perianal abscess 5.

Outcomes and Complications

The use of post-operative antibiotics can impact patient outcomes, including the risk of recurrence and complications.

• Inadequate antibiotic coverage after incision and drainage of complicated perianal abscesses resulted in a higher re-admission rate for abscess recurrence 2.
• The use of recommended antibiotics, as per the Surgical Infection Society/Infectious Disease Society of America guidelines, may shorten the time to defervescence and reduce the risk of a persistent abscess in patients undergoing percutaneous abscess drainage for a postoperative abscess after gastrointestinal surgery 6.

Special Considerations

Certain patient populations, such as those with underlying medical conditions or immunocompromised individuals, may require special consideration when it comes to post-operative antibiotics.

• The decision to use antibiotics in these patients should be made on a case-by-case basis, taking into account the individual patient's risk factors and medical history 3.