What antibiotics are recommended for a patient with a retained fish bone and risk of infection?

Antibiotic Recommendations for Retained Fish Bone

For a patient with a retained fish bone without signs of perforation or systemic infection, routine antibiotic prophylaxis is not recommended. 1

Clinical Assessment First

Before deciding on antibiotics, evaluate for:

• Signs of perforation: peritonitis, free air on imaging, hemodynamic instability 1
• Signs of infection: fever, elevated inflammatory markers (CRP, procalcitonin, lactate), leukocytosis, cellulitis 1
• Hemodynamic stability: vital signs, end-organ perfusion 1

Antibiotic Strategy Based on Clinical Presentation

No Perforation, No Infection Signs

Do not give antibiotics routinely. 1 The 2021 WSES-AAST guidelines explicitly recommend against routine antimicrobial therapy for retained anorectal foreign bodies without signs of infection or perforation, citing the global rise in antibiotic resistance. 1

Perforation or Hemodynamic Instability Present

Immediately initiate broad-spectrum intravenous antibiotics covering aerobic and anaerobic bacteria. 1

First-line regimen:

• Amoxicillin-clavulanate (ampicillin-sulbactam) IV 2, 3
• Alternative: Piperacillin-tazobactam 2

These agents provide coverage for:

• Gram-positive organisms (Staphylococcus, Streptococcus) 2
• Gram-negative organisms (Enterobacteriaceae) 2
• Anaerobes (Bacteroides species) 1, 2

High-Risk Patients Without Overt Infection

For immunocompromised patients, those with advanced liver disease, or significant tissue trauma, consider prophylactic amoxicillin-clavulanate for 3-5 days. 3 This falls within guideline recommendations for high-risk wounds with moderate to severe injuries. 3

Specific Antibiotic Dosing

Amoxicillin-clavulanate:

• IV: 1.2-2.4g every 6-8 hours 2
• Oral (if transitioning): 875/125mg twice daily 2, 4

Duration:

• With perforation/peritonitis: Continue until source control achieved, typically 3-5 days post-operatively 1
• Prophylaxis only: 3-5 days maximum 3

Critical Pitfalls to Avoid

• Do not use cloxacillin or flucloxacillin alone for fish bone injuries—these lack coverage for gram-negative and anaerobic bacteria commonly present in gastrointestinal perforations. 3, 5
• Do not delay surgical intervention while waiting for antibiotics to work—retained foreign bodies require removal, and antibiotics are adjunctive only. 1
• Do not extend prophylaxis beyond 5 days without documented infection, as this increases resistance without benefit. 3
• Obtain cultures before starting antibiotics if perforation is suspected, to guide de-escalation. 1

Special Considerations

If the fish bone has caused a perianal abscess (as documented in case reports), the priority is surgical drainage with foreign body removal, followed by antibiotics. 6 In this scenario, amoxicillin-clavulanate remains appropriate empiric coverage. 6

For marine-related injuries with concern for atypical organisms like Mycobacterium marinum, consider adding doxycycline or trimethoprim-sulfamethoxazole if chronic infection develops post-removal, though this is rare with acute fish bone injuries. 1