What is the recommended antibiotic regimen for the management of appendicitis?

Management of Appendicitis: Antibiotic Regimens

Surgical Patients: Perioperative Antibiotics

For patients undergoing appendectomy for uncomplicated appendicitis, administer a single preoperative dose of broad-spectrum antibiotics (0-60 minutes before incision) and do not continue antibiotics postoperatively. 1

Uncomplicated Appendicitis (Surgical Management)

• Single preoperative dose only - no postoperative antibiotics needed 1
• Recommended regimens for community-acquired infection 1:
  • Amoxicillin/clavulanate 1.2-2.2 g every 6 hours, OR
  • Ceftriaxone 2 g every 24 hours + metronidazole 500 mg every 6 hours, OR
  • Cefotaxime 2 g every 8 hours + metronidazole 500 mg every 6 hours
• For beta-lactam allergy: Ciprofloxacin 400 mg every 8 hours + metronidazole 500 mg every 6 hours OR moxifloxacin 400 mg every 24 hours 1
• Avoid ampicillin-sulbactam due to high E. coli resistance rates 1
• Avoid cefotetan and clindamycin due to increasing Bacteroides fragilis resistance 1

Complicated Appendicitis (Perforation/Abscess - Surgical Management)

Limit postoperative antibiotics to 3-5 days maximum when adequate source control is achieved. 1

• Continue broad-spectrum antibiotics postoperatively for 3-5 days only 1
• Same regimens as uncomplicated appendicitis (above) 1
• For ESBL risk: Ertapenem 1 g every 24 hours OR tigecycline 100 mg loading dose, then 50 mg every 12 hours 1
• Discontinue based on clinical improvement (resolution of fever, declining inflammatory markers), not arbitrary duration 1

Pediatric Considerations

• Uncomplicated appendicitis: Single preoperative dose only, no postoperative antibiotics 1
• Complicated appendicitis: Switch to oral antibiotics after 48 hours, total duration <7 days 1
• Ceftriaxone + metronidazole is equally effective as anti-pseudomonal regimens (piperacillin-tazobactam) for perforated appendicitis 2

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Non-Operative Management (Antibiotics-First Strategy)

Non-operative management with antibiotics is appropriate for selected patients with CT-confirmed uncomplicated appendicitis, but appendectomy remains the treatment of choice due to significant recurrence rates (approximately 23-30%). 1

Patient Selection for Non-Operative Management

• Appropriate candidates 1:

  • CT-confirmed uncomplicated appendicitis (appendix <13 mm diameter)
  • No appendicolith (presence increases failure rate significantly)
  • No mass effect
  • Hemodynamically stable
  • No signs of sepsis

• Contraindications 3:

  • Appendicolith on CT (≈40% failure rate)
  • Appendiceal diameter ≥13 mm
  • Mass effect
  • Patients unfit for potential rescue surgery

Antibiotic Regimen for Non-Operative Management

Administer minimum 48 hours IV antibiotics followed by oral antibiotics for total 7-10 days. 1

• Initial IV therapy (minimum 48 hours) 1:

  • Ertapenem 1 g every 24 hours (preferred in studies), OR
  • Amoxicillin/clavulanate 1.2-2.2 g every 6 hours, OR
  • Ceftriaxone 2 g every 24 hours + metronidazole 500 mg every 6 hours

• Followed by oral therapy to complete 7-10 days total 1, 4:

  • Ciprofloxacin + metronidazole, OR
  • Cefdinir + metronidazole

• Success rate: Approximately 70-77% avoid surgery at 1 year 3, 4

• Recurrence rate: 11-23% within first year 1, 4

Pediatric Non-Operative Management

• Only for selected children without appendicolith 1
• Same antibiotic regimens as adults (weight-based dosing) 1
• Higher failure rate (23%) compared to surgery 1
• Discuss risks/benefits with family including recurrence possibility 1

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Complicated Appendicitis with Abscess (Non-Operative Initial Management)

For periappendiceal abscess, percutaneous drainage plus antibiotics is preferred when interventional radiology is available; surgery is indicated when drainage is not feasible. 1

• Antibiotics alone for small abscesses (<3-4 cm) 1
• Percutaneous drainage + IV antibiotics for large abscesses 1
• Same antibiotic regimens as complicated appendicitis (above) 1
• No routine interval appendectomy for patients <40 years old unless recurrent symptoms 1
• For patients ≥40 years old: Colonoscopy and interval CT recommended due to 3-17% neoplasm risk 1

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Critical Illness/Healthcare-Associated Infection

For critically ill patients or healthcare-associated appendicitis, use carbapenem-based regimens with consideration for resistant organisms. 1

• Meropenem 1 g every 8 hours 1, 5, OR
• Doripenem 500 mg every 8 hours, OR
• Imipenem/cilastatin 1 g every 8 hours 1
• Add vancomycin or linezolid if VRE risk (prior VRE, immunocompromised, prolonged ICU stay) 1
• Consider antifungal coverage (echinocandins) for high-risk invasive candidiasis 1

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Key Pitfalls to Avoid

• Do not routinely use anti-pseudomonal antibiotics (piperacillin-tazobactam, cefepime) for uncomplicated community-acquired appendicitis - reserve for high-risk patients only 1, 6
• Do not continue postoperative antibiotics beyond 3-5 days even for complicated appendicitis with adequate source control 1
• Do not attempt non-operative management in patients with appendicolith - surgical failure rate approaches 40% 3
• Do not use aminoglycosides routinely due to toxicity when equally effective alternatives exist 1
• Enterococcal coverage is not necessary for community-acquired appendicitis 1