Cellulitis (DERM) Flashcards
Define cellulitis.
Acute spreading infection of the skin with visually distinct borders, that involves the deep dermis and subcutaneous tissue
What is the difference between cellulitis and erysipelas?
- cellulitis - involves deep dermis and subcutaneous tissue
- erysipelas - distinct form of superficial cellulitis involving only the upper dermis and superficial lymphatics –> raised and sharply demarcated from uninvolved skin
What is cellulitis characterised by?
Redness, swelling, heat and tenderness, and commonly occurs in an extremity
(Immunocompromised patients may present with atypical infections)
How does cellulitis develop?
- when microorganisms gain entry into dermal and subcutaneous tissues via disruptions in cutaneous barrier e.g. minor skin injury
- often results from: penetrating injury, local lesions (e.g. insect bites), fissuring (e.g. anal fissures)
What are the most common causative bacteria of cellulitis? (2)
- Staphylococcus aureus (catalase +ve)
- Streptococcus pyogenes (catalase -ve)
- beware of MRSA
What is orbital cellulitis usually caused by?
Haemophilus influenzae
What are the clinical features of cellulitis? (5)
- acute onset of red, painful, hot, swollen skin
- poorly defined (not well demarcated) lesions - compared to erysipelas –> well-demarcated, bright red raised skin
- most commonly occurs on shins
- Hx of cut/scratch/injury
- systemic symptoms - fever, chills, nausea, headache
What systemic symptoms can be seen in cellulitis? (4)
- fever
- chills
- nausea
- headache
How does erysipelas differ clinically to cellulitis?
- more superficial, limited version of cellulitis
- causes well-defined lesions + bright red raised skin
- caused by Streptococcus pyogenes
- treated with flucloxacillin
How does periorbital cellulitis present?
Painful swollen red skin AROUND the eye
How does orbital cellulitis present?
Painful or limited eye movements, VISUAL IMPAIRMENT
What might you see on examination of cellulitis?
- lesion: erythema, oedema, warm tender indistinct margins
- pyrexia - may suggest systemic spread
- NB exclude the presence of an abscess - aspirate if pus suspected
- orange-peel appearance, blistering, bleeding, lymphangitis (red line that spreads proximally along lymphatics towards lymph nodes)
- unilateral
- toe-to-web abnormalities (evidence of fungal infection AKA tinea may reveal the point of bacterial entry)
What are some risk factors for cellulitis?
DOOVE + skin break
- diabetes (–> poor vascularisation)
- obesity
- oedema (& lymphoedema)
- venous insufficiency (–> poor vascularisation)
- eczema
What observations show septic signs of cellulitis? (5)
- high HR
- high RR
- low BP
- confusion (low GCS)
- fever
What is a sign of systemic illness in cellulitis?
Pyrexia
How do we usually diagnose cellulitis?
Clinical diagnosis - only request further tests if there are signs of systemic illness or septicaemia
- acute, red, hot, swollen skin
- Hx trauma/cracked skin/scratch/injury
- Hx lymphoedema/poor vascularisation
What are the 1st-line investigations for cellulitis? (1 + 6)
- clinical diagnosis
- FBC
- ESR
- CRP
- U&Es
- blood culture and sensitivities - if patient needs admission
- skin swab/aspirate
What would bloods show for cellulitis?
High WCC and CRP/ESR
How can we identify the causative pathogen and know which Abx to use for cellulitis?
Blood MC&S and skin swab
When do we admit patients with cellulitis?
If septicaemia suspected, or if significant systemic upset and/or comorbidities
What do we do after admitting a patient with cellulitis?
Blood MC&S to identify pathogen and test antibiotic sensitivity - do before giving Abx
What imaging could we do for cellulitis? (2)
- XR - if osteomyelitis or necrotising fasciitis
- CT/MRI - if orbital cellulitis is suspected to check if infection has spread posteriorly to brain
What are some differentials for cellulitis?
- necrotising fasciitis - marked pain, necrotic bullous, crepitus, surgical exploration
- thrombophlebitis - tender palpable cord along affected vein
- DVT - prolonged immobility, tender vein
- gout
- Lyme disease
- contact dermatitis
- insect bites and stings
- fixed drug eruptions
- eosinophilic cellulitis
- sweet syndrome
- inflammatory carcinoma
- calciphylaxis
- lipodermatosclerosis (venous insufficiency)
What is the first thing you do with patients with cellulitis?
Exclude sepsis!!
- fever
- tachycardic
- hypotensive
- low O2 sats
- high respiratory rate
