Cellulitis

Reviewed and revised 24 May 2014

OVERVIEW

Cellulitis is an uncomplicated non-necrotizing acute infection of the skin involving the hypodermis (mid-to-lower dermis and subcutaneous tissue) and spares deeper structures such as fascia and muscle.

CAUSE

Typical organisms

  • Streptococcus pyogenes
  • Staphylococcus aureus

These risk factors confer a predisposition for cellulitis:

  • Diabetes mellitus.
  • Vascular insufficiency
  • Peripheral vascular disease
  • Chronic venous insufficiency
  • Chronic lymphoedema
  • loss of skin integrity, due to:
    • Penetrating trauma (including retained foreign bodies)
    • Insect or animal bites
    • Chronic inflammatory dermatoses (such as psoriasis or eczema)
    • Chronic skin infections (e.g. Tinea)
  • Radiotherapy

CLINICAL FEATURES

Cellulitis typically has these features

  • Acute onset
  • Painful erythematous area of inflamed skin (not elevated, ill defined demarcation boundary)
  • tender and warm on palpation
  • most common on the lower limbs
  • rarely bilateral

If more severe

  • Lymphangitis
  • Lymphadenopathy
  • Systemic features: fever and constitutional symptoms (e.g. headache, malaise, lethargy, anorexia)

Follows usual natural history

  •  progression of erythema +/- fever  up to 72 hours after starting appropriate antibiotics
  •  erythema gradually resolves over weeks, discolouration persists for months in some cases

Risk factors may be present

DIFFERENTIAL DIAGNOSIS

  • Erysipelas
    • a superficial variant of cellulitis involving only the upper dermis and superficial cutaneous lymphatics.
    • characterised by a well demarcated area of erythema raised above the level of the surrounding skin
  • Deeper infections
    • these are far more serious and may involve fascia (e.g. necrotizing fasciitis) or muscle (e.g. pyomyositis, clostridial myonecrosis/ gangrene)
    • severe pain, systemically unwell, +/- subcutaneous crepitus, rapidly progressive
  • Lipodermatosclerosis
    • chronic erythema and pain with episodic exacerbation in patients with venous insufficiency
    • typically bilateral, lacks systemic features and not warm to touch
  • stasis dermatitis
  • contact dermatitis
  • lymphoedema
  • eosinophilic cellulitis (Well’s syndrome)
  • papular urticaria
  • fixed drug reactions
  • burns

INVESTIGATIONS

  • Usually only needed systemically unwell, severe or uncertain  of diagnosis

Laboratory tests

  •  FBE, CRP, UEC, glucose

Imaging

  • XR to exclude foreign body
  • U/S to exclude foreign body, rule out abscess; may show marbling appearance of cellulitis, diagnose soft tissue gas forming infections
  • CT/MRI if need to exclude fasciitis or myonecrosis (must not delay operative therapy if indicated)

MANAGEMENT

Resuscitation

  • if indicated

Specific antibiotic therapy (Adjust does in renal/ hepatic dysfunction)

  • oral antibiotics for uncomplicated cellulitis
    • Flucloxacillin 1g q6h for 7-10d or cephalexin 1g q6h for 7-10d
    • If immediate penicillin hypersensitivity:  Clindamycin 450 mg orally 8 hourly, (7-10 days)
  • IV Antibiotics for failure of oral antibiotics or complicated cases
    • Flucloxacillin 1-2g IV q6h or Cephazolin 1-2g IV q8h
    • If immediate penicillin hypersensitivity: Clindamycin 450 mg IV q8h or  Vancomycin 1.5g IV q12h

Supportive care and monitoring

  • Resting and elevating (where possible) the effected part; can consider the use of a POP backslab
  • Analgesia (oral may be sufficient)

DISPOSITION

Admission to hospital is generally warranted if:

  • significant co-morbidities (especially if immunosuppressed)
  • unable to tolerate oral medication
  • social issues that impact care and GP follow up
  • complications (e.g. systemically unwell, trauma/ need for debridement, deep soft tissue infections)
  • special sites (periorbital, perineal)

The appropriate admitting team may vary between hospitals

  • observation ward
  • hospital in the home
  • general medicine
  • general surgery

Surgical consult if:

  • suspected deep soft tissue infection
  • face or hands (usually Plastics)
  • periorbital or orbital cellulitis (Ophthalmology)
  • peritonsillar cellulitis (ENT)

References and links

Journal articles

  • Adhikari S, Blaivas M. Sonography first for subcutaneous abscess and cellulitis evaluation. J Ultrasound Med. 2012 Oct;31(10):1509-12. PubMed PMID: 23011612.
  • Keller EC, Tomecki KJ, Alraies MC. Distinguishing cellulitis from its mimics. Cleve Clin J Med. 2012 Aug;79(8):547-52. doi: 10.3949/ccjm.79a.11121. PubMed PMID: 22854433.
  • Phoenix G, Das S, Joshi M. Diagnosis and management of cellulitis. BMJ. 2012 Aug 7;345:e4955. PMID: 22872711.

CCC 700 6

Critical Care

Compendium

Chris is an Intensivist and ECMO specialist at The Alfred ICU, where he is Deputy Director (Education). He is a Clinical Adjunct Associate Professor at Monash University, the Lead for the  Clinician Educator Incubator programme, and a CICM First Part Examiner.

He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives. He was one of the founders of the FOAM movement (Free Open-Access Medical education) has been recognised for his contributions to education with awards from ANZICS, ANZAHPE, and ACEM.

His one great achievement is being the father of three amazing children.

On Bluesky, he is @precordialthump.bsky.social and on the site that Elon has screwed up, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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