What is the appropriate management for a patient with swelling under the toes on the plantar aspect of the foot, considering potential underlying conditions and possible history of Impaired renal function or liver disease?

Management of Plantar Swelling Under the Toes

In a patient with swelling under the toes on the plantar aspect of the foot, immediately assess for diabetic foot infection (DFI), particularly if the patient has diabetes, renal impairment, or liver disease, as this represents a potentially limb-threatening condition requiring urgent evaluation and treatment. 1

Initial Assessment Priority

Rule Out Diabetic Foot Infection First

• Examine for signs of infection: erythema extending >2 cm around any wound, purulent discharge, warmth, tenderness, fever, or systemic signs (tachycardia, elevated white blood cell count, elevated CRP) 1
• Perform probe-to-bone test if any ulceration is present—a positive test (feeling hard, gritty bone with a sterile blunt probe) strongly suggests osteomyelitis, especially in high-risk patients 1
• Check for limb-threatening signs: rapid progression, extensive necrosis, crepitus, new wound anesthesia, pain out of proportion to findings, or critical limb ischemia 1
• Assess vascular status: palpate dorsalis pedis and posterior tibial pulses; if absent or diminished, obtain ankle-brachial index (ABI) or toe-brachial index (TBI) 1

Critical Red Flags Requiring Urgent Surgical Consultation

• Plantar wound with dorsal erythema or fluctuance (suggests infection through fascial compartments) 1
• Fever with plantar swelling and elevated inflammatory markers (WBC >15, CRP >100) 1
• Any visible bone or probe-to-bone positive test 1
• Absent pulses with TBI <0.7 or ABI <0.4 1

Diagnostic Workup

Immediate Studies

• Plain radiographs of the affected foot (weight-bearing if possible) to evaluate for osteomyelitis, bony deformities, Charcot foot, or foreign bodies 1
• Laboratory tests: complete blood count, CRP, erythrocyte sedimentation rate (ESR), glucose level, renal function 1
• Monofilament testing to assess for loss of protective sensation (peripheral neuropathy) 1

If Infection Suspected

• Obtain wound cultures from deep tissue after debridement (not superficial swabs) before starting antibiotics 1
• Blood cultures if systemic signs present 1
• MRI is the gold standard for diagnosing osteomyelitis if plain films are negative but clinical suspicion remains high 1

Treatment Algorithm

For Diabetic Foot Infection (Most Critical Scenario)

Immediate Management:

• Admit to hospital if moderate-to-severe infection (systemic signs, deep tissue involvement, or failed outpatient therapy) 1
• Start empiric IV antibiotics immediately after cultures obtained: amoxicillin-clavulanate or similar broad-spectrum coverage 1
• Urgent surgical debridement within 24 hours if no improvement, purulent discharge increases, or deep infection suspected 1
• Strict offloading with non-removable knee-high device (total contact cast) or removable walker if patient adherent 1

Definitive Management:

• Narrow antibiotics based on culture results (e.g., flucloxacillin 1g four times daily for Staphylococcus aureus) 1
• Duration: 2 weeks for soft tissue infection without bone involvement; 4-6 weeks if osteomyelitis present 1
• Surgical intervention may include debridement, limited resection, or amputation depending on extent 1

For Non-Infectious Causes

If plantar fasciitis suspected (stabbing pain worse in morning, tenderness at medial calcaneus):

• Plantar fascia stretching exercises and ice massage 2
• NSAIDs for pain control 2
• Avoid night splints and orthoses initially as evidence is limited 2

If plantar vein thrombosis suspected (unilateral pain, swelling, heavy feeling):

• Compression ultrasound or MRI for diagnosis 3
• Treatment: rest, NSAIDs, consider anticoagulation for 6 months in confirmed cases 3

Special Considerations for Renal/Liver Disease

• Adjust antibiotic dosing for renal impairment (reduce flucloxacillin dose if creatinine clearance <30 mL/min) 1
• Avoid nephrotoxic agents (aminoglycosides, vancomycin) unless absolutely necessary with close monitoring 1
• Monitor for fluid overload in patients with renal or liver disease during IV therapy 1
• Check coagulation status before any surgical intervention in liver disease patients 1

Prevention and Long-Term Management

• Daily foot inspection by patient or caregiver, especially between toes 1, 4
• Proper footwear: therapeutic shoes with demonstrated 30% plantar pressure reduction for high-risk patients 1
• Never walk barefoot or in thin-soled slippers, even at home 1, 4
• Glycemic control optimization to prevent progression of neuropathy and infection 1
• Multidisciplinary foot clinic follow-up including podiatry, endocrinology, and vascular surgery as needed 1

Common Pitfalls to Avoid

• Do not delay surgical consultation for plantar infections—the plantar surface is the most common site for severe foot infections requiring urgent intervention 1
• Do not rely on absence of fever or leukocytosis to rule out serious infection in diabetic or immunocompromised patients 1
• Do not use superficial wound swabs for culture—these are unreliable and lead to inappropriate antibiotic selection 1
• Do not apply moisturizing creams between toes—this increases maceration risk and fungal/bacterial infection 4
• Do not assume adequate perfusion based on palpable dorsalis pedis pulse alone if posterior tibial pulse is absent—obtain objective vascular studies 1