Contents
Introduction
Cellulitis is caused by bacterial infection of the dermis layer of the skin and the deeper subcutaneous tissues. Often the infection is due to a break or puncture to the skin which allows bacteria to enter, however in some cases no obvious break to skin integrity can be located.
The most common sites for cellulitis to occur are the legs and face, although cellulitis can cause infection to any area of skin. Typically the presentation is of unilateral leg symptoms following a break to the skin.
Cellulitis infections are often minor requiring primary care management, however in elderly patients or those with significant co-morbidities, cellulitis can be of great morbidity and mortality.
Epidemiology
Very common infection presenting to primary, secondary and emergency care
Incidence of 24.6/1000
Risk Factors
- Wounds to the skin
- Diabetes
- Old age
- Insect bites
- Obesity
- Fungal infections between toes
- Skin conditions such as eczema
- Chronically swollen legs (e.g. lymphoedema)
- Chronic venous insufficiency
- Varicose veins
- Intravenous drug user
- Immunosuppression
- Previous cellulitis
Aetiology
Most common causative organisms are:
- Group A beta-haemolytic streptococci – Streptococcus pyogenes
- Staphylococcus aureus
Less commonly:
- Streptococcus pneumonia
- Haemophilus influenza – Often in infants prior to Hib vaccination
- Gram negative bacilli
- Anaerobes
Symptoms
- Often in the lower limbs, effecting one leg
- Symptoms spread quickly
- Erythema (rubor) – blends into surrounding skin. “Tracking” can occur along blood vessels and tends to spread more quickly than generalised erythema
- Pain (dolor)
- Swelling (tumor)
- Warmth of effected skin (calor)
- Often a site of skin damage – ulcer, wound, bite mark, injection site
- Systemic effects – fever, malaise, nausea, rigors, confusion in the elderly
Differentials
- DVT
- Varicose eczema
- Ruptured Baker’s cyst
- Necrotizing fasciitis
- Metastatic cancer (carcinoma erysipeloides)
Investigations
Primary Care
Not usually required
Diagnosis can be made on clinical history and examination alone
If there is an obvious wound in the skin with discharge then this may be swabbed
Secondary Care
Bloods – Raised WCC, CRP, fasting glucose, lipids, cholesterol
Blood cultures – Identify the causative organism and direct antibiotic choice
X-ray, CT, MRI – If concerns of deeper infection and/or foreign body in situ
Treatment
General considerations:
Send to hospital if:
- Significantly unwell with symptoms such as tachycardia, tachypnoea, hypotension, vomiting, or acute confusion
- Unstable co-morbidities such as uncontrolled diabetes
- Contaminated wound
- Limb threatening infection due to vascular compromise
- Sepsis or life threatening complications such as necrotizing fasciitis
- Very young (<1 years) or frail
- Immunocompromised
- Gross limb swelling
- Facial cellulitis
- Periorbital cellulitis
If minor/mild cellulitis and is being treated by GP:
PO Flucloxacillin 500mg QDS for 7 days
Or if penicillin allergic
PO Erythromycin 500 QDS or Clarithromycin 500 mg BD for 7 days
For cases requiring management in hospital:
Flucloxacillin 1 gram QDS IV (For 48 hours, then r/v if can be stepped down to oral)
Or if penicillin allergic
Clindamycin 600mg QDS IV (For 48 hours, then r/v if can be stepped down to oral)
If case may have been contaminated by fresh or salt water consult microbiology
Complications
Acute
- Abscess formation
- Sepsis
- Myositis / Osteomyelitis
- Necrotizing fasciitis – consider if pain is not being eased by analgesia!!
- If around the eye can spread to cause meningitis
- Post streptococcal nephritis
Chronic
- Persistent leg ulceration
- Chronic lymphoedema
Prognosis
Vast majority of patients will make a complete and uncomplicated recovery
Recurrence rates of cellulitis have been reported between 11-16%
References
- Murtagh’s General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt
- Oxford Handbook of General Practice. 3rd Ed. (2010) Simon, C., Everitt, H., van Drop, F.
- Beers, MH., Porter RS., Jones, TV., Kaplan JL., Berkwits, M. The Merck Manual of Diagnosis and Therapy