What is the appropriate workup and treatment for a patient presenting to the Emergency Department (ED) with a wound on the calf and purulent drainage?

Emergency Department Workup for Calf Wound with Purulent Drainage

The most important initial step in managing a patient with a calf wound with purulent drainage is to open the wound, evacuate the infected material, obtain appropriate cultures, and begin empiric antibiotic therapy based on the severity of infection.

Initial Assessment

Clinical Evaluation

• Assess vital signs: temperature, heart rate, blood pressure, respiratory rate
• Evaluate wound characteristics:
  • Size and depth of wound
  • Extent of erythema and induration beyond wound margins
  • Character and amount of purulent drainage
  • Presence of necrotic tissue
  • Probe the wound to determine depth and potential involvement of deeper structures
• Check for systemic signs of infection:
  • Fever >38.5°C
  • Heart rate >110 beats/minute
  • Leukocytosis (WBC >12,000 cells/μL)

Severity Classification

Classify infection severity to guide management 1:

1. Mild infection: Local infection with <2 cm of erythema, limited to skin/subcutaneous tissue
2. Moderate infection: Erythema >2 cm, deeper tissue involvement (fascia, muscle, tendon, joint, bone)
3. Severe infection: Systemic inflammatory response syndrome (SIRS) or metabolic instability

Diagnostic Workup

Laboratory Tests

• Complete blood count with differential
• Basic metabolic panel
• C-reactive protein and/or erythrocyte sedimentation rate
• Blood cultures (if severe infection or systemic symptoms present) 1
• Wound cultures:
  • Cleanse and debride the wound before obtaining specimens
  • Obtain tissue specimens from the debrided base via curettage or biopsy (preferred)
  • Avoid swabbing undebrided wounds or wound drainage 1

Imaging

• Plain radiographs of the affected limb to assess for:
  • Foreign bodies
  • Gas in soft tissues
  • Underlying bone involvement
• Consider advanced imaging for moderate to severe infections:
  • MRI (best for soft tissue and bone marrow evaluation)
  • CT scan (if MRI contraindicated or unavailable)

Treatment Approach

Wound Management

1. Incision and drainage: The most important initial therapy for a wound with purulent drainage is to open the incision, evacuate the infected material, and continue dressing changes until the wound heals by secondary intention 1
2. Wound irrigation: Use clean tap water or sterile normal saline to irrigate the wound thoroughly 2
3. Debridement: Remove all necrotic tissue and foreign material 1

Antibiotic Therapy

Based on severity of infection 1:

1. Mild infection:

   • If <5 cm of erythema/induration and minimal systemic signs, antibiotics may be unnecessary after proper drainage
   • If antibiotics indicated: oral agent with Staphylococcus aureus coverage (e.g., cephalexin, dicloxacillin)

2. Moderate infection:

   • Empiric coverage for gram-positive cocci (including MRSA if risk factors present) and gram-negative bacilli
   • Options: amoxicillin-clavulanate, ceftriaxone plus metronidazole, or fluoroquinolone plus clindamycin

3. Severe infection:

   • Broad-spectrum parenteral therapy: vancomycin or linezolid plus piperacillin-tazobactam or a carbapenem 1
   • Duration typically 7-14 days depending on clinical response

Special Considerations

• Diabetic patients: Require more aggressive management due to impaired wound healing and higher risk of complications 1

  • Lower threshold for imaging to rule out osteomyelitis
  • Evaluate peripheral perfusion to assess need for vascular consultation 1
  • Consider multidisciplinary approach including infectious disease, podiatry, and vascular surgery

• Vascular assessment: Evaluate peripheral pulses, ankle-brachial index, or toe pressures in patients with risk factors for peripheral arterial disease 1

Disposition

• Admission criteria 1:

  • Systemic toxicity (fever, leukocytosis)
  • Metabolic instability
  • Rapidly progressive or deep tissue infection
  • Substantial necrosis or gangrene
  • Critical ischemia
  • Inability to care for self or inadequate home support

• Outpatient management:

  • Mild infections with adequate drainage
  • Reliable patient with good follow-up capability
  • Clear instructions for wound care and antibiotic administration
  • Follow-up within 48-72 hours

Common Pitfalls to Avoid

1. Inadequate drainage: "Don't let the sun set on pus" - complete drainage of purulent material is essential for infection control 1
2. Reliance on superficial wound swabs: These have higher risk of contamination with normal skin flora; tissue culture or curettage of the wound base is preferred 1
3. Delayed surgical consultation: Prompt surgical consultation is recommended for aggressive infections with systemic toxicity or suspicion of necrotizing infection 1
4. Failure to assess vascular status: Peripheral artery disease is present in about 50% of diabetic foot ulcers and is associated with delayed wound healing and amputation 1
5. Overlooking osteomyelitis: Consider bone involvement if the wound is chronic, deep, or located over a bony prominence

By following this systematic approach to the workup and management of calf wounds with purulent drainage, clinicians can effectively treat these infections while minimizing complications and optimizing outcomes.