Cellulitis

Cellulitis is defined as a bacterial infection of the dermis and subcutaneous tissue. It is often caused by a break in the skin, which allows bacteria to enter. It commonly affects the legs and face, though it can infect any area of skin. Infection is often minor; however, in elderly patients and in those with comorbidities, there is increased morbidity and mortality. Diagnosis is clinical.

Very common infection. Incidence of 24.6 per 1000 people.

• Risk factors for cellulitis
  • Wound to the skin
  • Diabetes
  • Immunosuppression
  • Intravenous drug user
  • History of cellulitis
  • Elderly
  • Obesity
  • Fungal infection
  • Skin condition, e.g., eczema
  • Lymphoedema or a chronically swollen leg
  • Chronic venous insufficiency
  • Varicose vein
• Common organisms
  • Group A Streptococcus
  • Staphylococcus aureus
• Patient History
  • Unilateral leg symptoms following a break in the skin
• Signs and symptoms
  • ErythemaPainSwellingWarmthSite of skin damage (ulcer, wound, bite mark, injection site)Systemic symptoms may be present: fever, malaise, nausea, rigors, and confusion
  Often unilateral. Erythema and swelling are Ill-defined
• Differentials
  • Deep Venous Thrombosis
  • Necrotizing Soft Tissue Infection (NSTI)
  • Varicose eczema
  • Metastatic cancer (Carcinoma erysipeloides)
• Investigations
  • CBC: raised WBC count
  • CRP: elevated
  • Other labs: fasting glucose, lipids, cholesterol
  • Blood culture and pus swabs: to identify the causative organism and select antibiotics
  • Imaging e.g X-ray: if there is a concern of deeper infection, e.g., NSTI or foreign body in situ
• Treatment
  • Analgesia
  • Elevate the legs
  • Tetanus vaccination
  • Mild cellulitis: PO Flucloxacillin, Erythromycin, or Clarithromycin
  • Severe cellulitis: IV Flucloxacillin or Clindamycin
• Indications for hospitalisation
  • Significantly unwell with systemic symptoms: tachycardia, tachypnoea, hypotension, vomiting, acute confusion
  • Unstable comorbidity, e.g., uncontrolled diabetes
  • Contaminated wound
  • Limb-threatening infection due to vascular compromise
  • Sepsis
  • Very young or frail
  • Immunocompromised
  • Gross limb swelling
  • Facial cellulitis
  • Periorbital cellulitis
• Acute complications
  • Abscess
  • Sepsis
  • Myositis
  • Osteomyelitis
  • NSTI
  • Meningitis
  • Post-streptococcal glomerulonephritis
• Chronic complications
  • Chronic leg ulcer
  • Chronic lymphoedema