What could be causing the recent onset of swelling in the feet and legs, considering the patient's current medications and medical history?

Differential Diagnosis of Bilateral Lower Extremity Swelling with Fluid Discharge

Dylan's bilateral leg and foot swelling with white fluid discharge most likely represents chronic venous insufficiency with secondary cellulitis, given his recurrent antibiotic use (amoxicillin and flucloxacillin) and the presence of fluid weeping from the skin. 1

Primary Diagnostic Considerations

Infection-Related Causes (Most Urgent)

Cellulitis with chronic edema is the most immediate concern, particularly given:

• Recent antibiotic prescriptions (amoxicillin dispensed 4 weeks ago, flucloxacillin 5 weeks ago) 2
• White fluid discharge suggesting wound exudate or purulent material 2
• Bilateral distribution with redness 2

Clinical features requiring immediate assessment include:

• Erythema extending >0.5 cm from any wound margins 2
• Local warmth, tenderness, or swelling 2
• Systemic signs: fever >38°C, heart rate >90 bpm, respiratory rate >20 breaths/min, or WBC >12,000/mm³ 2
• Any skin breakdown or ulceration with purulent discharge 2

Chronic Venous Insufficiency

This is the most common cause of bilateral leg edema in adults and frequently predisposes to infection. 1, 3 Key features include:

• Pitting edema that worsens with prolonged standing 1
• Hemosiderin staining (brownish discoloration) 1
• Skin induration and lipodermatosclerosis 1
• Weeping of clear or white fluid (venous stasis dermatitis) 2

Medication-Induced Edema

Several of Dylan's medications can cause or exacerbate lower extremity swelling:

• Diazepam (benzodiazepines can contribute to fluid retention) 3
• This is particularly relevant given his twice-daily dosing for 22 months 3

Critical Diagnostic Algorithm

Immediate Assessment (Same Visit)

Examine for infection severity classification: 2

1. Mild infection: Erythema <2 cm around any wound, no systemic symptoms
2. Moderate infection: Erythema ≥2 cm or deeper tissue involvement without systemic symptoms
3. Severe infection: Any systemic inflammatory response (fever, tachycardia, elevated WBC)

Check for pitting versus non-pitting edema: 1

• Pitting edema suggests venous insufficiency, heart failure, or medication effect
• Non-pitting with firm texture indicates advanced lymphedema or chronic changes

Assess bilaterality pattern: 1

• Bilateral symmetric: systemic causes (cardiac, renal, hepatic, medication)
• Asymmetric or unilateral component: venous insufficiency or infection more likely

Essential Diagnostic Workup

Laboratory evaluation should include: 1

• Complete blood count (WBC to assess infection) 2
• BNP/NT-proBNP (to exclude heart failure as cause) 2, 1
• Renal function, liver function, albumin (systemic causes) 1
• Wound culture if any skin breakdown present (tissue sample preferred over swab) 2, 1

Imaging studies: 2, 1

• Duplex Doppler ultrasound as initial evaluation to assess venous system 1
• Plain radiographs if concern for underlying osteomyelitis with chronic wounds 2
• MRI with contrast if deep soft tissue infection suspected 2, 1

Management Approach

If Infection Present

Initiate empiric antibiotics immediately if moderate or severe infection: 2

• Flucloxacillin 500mg-1g four times daily for Staphylococcus aureus coverage 2
• Add metronidazole 400mg three times daily if anaerobic coverage needed 2
• Duration: minimum 2 weeks for soft tissue infection 2

Admission criteria: 2

• Systemic inflammatory response syndrome present
• Failed outpatient antibiotic therapy
• Rapidly progressive erythema or swelling
• Concern for deeper infection or osteomyelitis

If Venous Insufficiency Primary

Conservative management includes: 3

• Leg elevation above heart level when resting 3
• Compression stockings (30-40 mmHg) once infection excluded 3
• Diuretics may be considered but address underlying cause first 3

Critical Pitfalls to Avoid

Do not dismiss bilateral swelling as purely systemic without examining for infection, as cellulitis can be bilateral and the white fluid discharge strongly suggests local pathology. 2, 1

Do not start compression therapy if active infection present, as this can worsen tissue perfusion and spread infection. 3

Consider discontinuing or reducing diazepam if no infection found and venous insufficiency confirmed, as benzodiazepines may contribute to edema. 3

The recurrent antibiotic prescriptions (6 amoxicillin dispenses, 2 flucloxacillin dispenses) suggest either recurrent infections or inadequately treated initial infection, warranting aggressive evaluation for underlying causes including venous insufficiency, diabetes screening, and immunocompromise. 2