How to manage a finger infected with a retained fish bone, presenting with swelling, pain, and mild purulent discharge?

Management of Fish Bone Injury with Infection in Finger

Immediate surgical exploration and debridement is required, combined with empiric antibiotics covering Staphylococcus aureus and aquatic organisms, as fish bone injuries frequently leave retained foreign material that causes disproportionate morbidity and requires surgical removal even when radiographs are negative. 1, 2

Immediate Assessment and Wound Exploration

• Perform surgical exploration with a sterile probe to assess wound depth, detect retained fish bone fragments, and evaluate for deeper structure involvement (tendon, bone, joint) 1
• Fish bone injuries commonly leave residual organic foreign material in tissues that drives persistent infection, even when not visible on imaging 2
• Radiographs are unreliable - they revealed radiolucent fish bone foreign bodies in only 2 of 5 patients in one series, meaning negative imaging does not exclude retained material 2
• Obtain tissue samples (not superficial swabs) from the wound for culture before starting antibiotics to identify the causative organism 1

Surgical Debridement

• All infected fish bone injuries except simple cellulitis require surgical debridement 2
• In the largest reported series, 8 of 9 patients with fish bone hand infections required surgical exploration, and one patient needed three separate debridements before the foreign body was finally removed 2
• Single surgical procedure was adequate in only 5 of 8 cases, highlighting that these infections can be more extensive than initially apparent 2
• The presence of purulent discharge indicates established infection requiring immediate drainage 3

Antibiotic Selection

Start empiric antibiotics immediately after obtaining cultures:

• Amoxicillin-clavulanate 875/125 mg twice daily is the first-line choice as it covers both typical skin flora (Staphylococcus aureus, Streptococcus) and aquatic organisms 4
• Add doxycycline 100 mg twice daily for broader coverage of aquatic pathogens - this combination was used in 96.7% of hospitalized fish bone injury cases 5
• Consider adding ceftazidime for severe infections or immunocompromised patients, as it was used in 68.8% of hospitalized cases 5
• Duration: 7-10 days minimum for established infection with purulent discharge 4

Rationale for Antibiotic Coverage

• Fish bone injuries can introduce unusual aquatic organisms beyond typical skin flora 2, 5
• Cultures from fish bone injuries yield organisms in only 40% of cases when obtained, but antibiotic selection should still cover the expected spectrum 5
• Tailor antibiotics once culture results return to target the specific causative organism 2

Tetanus Prophylaxis

• Administer tetanus toxoid booster if >5 years since last dose, as this is a contaminated puncture wound 4

Critical Warning Signs Requiring Urgent Escalation

Watch for these complications that indicate deeper involvement:

• Flexor tendon sheath infection (pain with passive extension, fusiform swelling along tendon) - two patients in one series required ray amputation due to this complication 2
• Pain disproportionate to visible injury suggests bone or periosteal involvement 4
• Fever or systemic signs - independently correlated with complicated hospitalization course (p=0.0005) 5
• Hypothenar or thenar space involvement requires aggressive surgical drainage 2

Special Considerations for Fish Bone Injuries

• These injuries cause morbidity out of proportion to the original wound due to retained organic material 2, 6
• Infections can be more extensive than expected from such small wounds, with severe tissue necrosis reported 6
• Immunocompromised patients (diabetes, liver disease, chronic steroids, malignancy) have significantly higher risk of complicated course (p=0.035) and require more aggressive management 5
• Rare fungal infections like sporotrichosis can occur from fish spine injuries, presenting with nodular lymphangitic spread 7

Follow-up Protocol

• Mandatory reassessment within 24 hours to evaluate response to treatment 4
• Elevation of the hand for first few days to reduce swelling 4
• If no improvement after initial debridement, plan for repeat surgical exploration - foreign body may still be present 2
• Overall prognosis is favorable with appropriate surgical and antibiotic management, with no deaths or amputations in the largest series of 122 cases 5

Common Pitfalls to Avoid

• Do not rely on negative radiographs to exclude retained foreign body - fish bones are often radiolucent 2
• Do not treat with antibiotics alone without surgical exploration when infection is established - the foreign material must be removed 2
• Do not underestimate the extent of infection - these small wounds can cause deep space infections requiring multiple debridements 2, 6
• Do not use superficial wound swabs for culture - obtain deep tissue samples during surgical exploration 1