Foot Cellulitis

Foot cellulitis is acute bacterial infection of the skin and subcutaneous tissue of the foot, usually from beta haemolytic streptococci and Staphylococcus aureus entering through tinea pedis, interdigital fissures, puncture wounds, ulcers or insect bites. In diabetes it is polymicrobial and can threaten the limb.

• Risk factors: diabetes, peripheral neuropathy, peripheral arterial disease, lymphoedema, obesity, barefoot walking, previous cellulitis.
• Common in rural Kenya with open footwear and soil exposure.

Warm, red, swollen, tender foot, sometimes with maceration between toes, fever and lymphangitic streaks up the leg.

• Differential diagnosis: gout, Charcot foot, deep vein thrombosis, contact dermatitis, stasis dermatitis, osteomyelitis, necrotising fasciitis, podoconiosis (non filarial elephantiasis, common in highland Kenya), mycetoma, tungiasis, erythromelalgia.
• Complications: abscess, osteomyelitis, septic arthritis, gangrene, necrotising infection, sepsis, recurrent infection, lymphoedema, amputation.

Clinical, with examination of the toe webs, sole and pulses.

• Full blood count, CRP, glucose, creatinine; blood cultures if febrile; deep swab of any wound.
• Radiograph (foreign body, gas, bone changes); ultrasound or MRI for abscess or osteomyelitis; ankle brachial index in diabetes.

Treat infection, remove the portal of entry and elevate.

• Supportive: elevation, rest, analgesia (paracetamol 1 g), mark the margin, dry between the toes, tetanus toxoid if due.
• Pharmacological: flucloxacillin 500 mg to 1 g four times daily for 7 days (cefalexin 500 mg four times daily; clindamycin 300 to 450 mg three times daily if penicillin allergic); tinea pedis: terbinafine 1 percent cream twice daily for 2 weeks. Diabetes or severe: amoxicillin clavulanate 1.2 g IV every 8 hours, or ceftriaxone 2 g IV daily with metronidazole 500 mg IV every 8 hours; add vancomycin 15 to 20 mg/kg IV every 12 hours for MRSA.
• Procedures: drainage of abscess; debridement of necrosis; surgical review for bone infection.
• Special groups: pregnancy, flucloxacillin or cefalexin; diabetes, admit if moderate or severe and control glucose; children, flucloxacillin 12.5 to 25 mg/kg four times daily; podoconiosis, foot hygiene and compression.
• Red flags: dusky skin, bullae, crepitus, exposed bone, absent pulses, fever with hypotension, no improvement at 48 hours.
• Follow-up: review at 48 to 72 hours; treat tinea; foot care and well fitting closed footwear.