Which physical findings suggest cellulitis and which indicate severe infection?

Updated: Jun 14, 2019
  • Author: Thomas E Herchline, MD; Chief Editor: Michael Stuart Bronze, MD  more...
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The physical examination should first focus on the area of concern. Nonpurulent cellulitis is associated with 4 cardinal signs of infection: erythema, pain, swelling, and warmth. Several physical examination findings may help the clinician identify the most likely pathogen and assess the severity of the infection, thereby facilitating appropriate treatment. Those findings include the following:

  • The involved site(s)is/are red, hot, swollen, and tender

  • Unlike erysipelas, the borders are not elevated or sharply demarcated

  • The involved site is the leg, which is the most common site [46, 61]

  • Regional lymphadenopathy is present

  • Malaise, chills, fever, and toxicity are present

  • Skin infection without underlying drainage, penetrating trauma, eschar, or abscess is most likely caused by streptococci; on the other hand, S aureus, often community-acquired methicillin-resistant S aureus (CA-MRSA), is the most likely pathogen when these factors are present [1]

  • Perianal cellulitis is usually observed in children with perianal fissures; it is characterized by perianal erythema and pruritus, purulent secretions, painful defecation, and blood in the stools [62]

  • Cellulitis characterized by violaceous color and bullae suggests more serious or systemic infection with organisms such as V vulnificus (see the image below) or S pneumoniae

    Cellulitis due to documented Vibrio vulnificus inf Cellulitis due to documented Vibrio vulnificus infection. (Image courtesy of Kepler Davis.)
  • Lymphangitic spread (red lines streaking away from the area of infection), crepitus, and hemodynamic instability are indications of severe infection, requiring more aggressive treatment

  • Circumferential cellulitis or pain that is disproportional to examination findings should prompt consideration of severe soft-tissue infection

The IDSA indicates that the following are also signs/symptoms of potentially severe deep soft-tissue infection (Note: these frequently appear later in the course of necrotizing infections), which necessitate emergent surgical evaluation [2] :

  • Violaceous bullae

  • Cutaneous hemorrhage

  • Skin sloughing

  • Skin anesthesia

  • Rapid progression

  • Gas in the tissue

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