Cellulitis and Soft Tissue Infections Author: Dennis L. Stevens, PhD, MD; Lawrence J. Eron, MD, FACP
Editorial changes - 2008-08-20
Author information and module status
Prevention
Screening
Diagnosis
Consultation for Diagnosis
Hospitalization
Non-drug Therapy
Drug Therapy
Patient Education
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Glossary
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Diagnosis
  • Obtain key elements of history to determine the severity and cause of the infection.
  • Use the physical exam to determine the severity and cause of the infection.
  • Recognize that underlying comorbid illness can affect the clinical presentation of cellulitis and soft tissue infection.
  • Use laboratory tests to document infection, judge the severity of illness, determine the cause, and guide initial and definitive antibiotic therapy.
  • Recognize that soft tissue infections can be caused by a number of different organisms, and are sometimes confused with noninfectious disease processes.
History and Physical Examination Elements for Soft Tissue Infection (table)
Laboratory and Other Studies for Aggressive Soft Tissue Infection  (table)
Differential Diagnosis of Soft Tissue Infection (table)

Obtain key elements of history to determine the severity and cause of the infection. C

  • Ask patients with soft tissue infection about a history of:
    • Previous cellulitis in the same area
    • Recurrent or persistent furunculosis
    • Diabetes
    • Tinea pedis
    • Saphenous vein bypass surgery
    • Chronic lymphedema
    • Venous stasis
    • Eczema
    • Psoriasis
  • Ask about proximate predisposing factors to infection, such as:
    • Recent surgery or traumatic injury
    • Animal, human, or insect bites
    • Use of new topical products
    • Exposure to animals
    • Currently used medications
    • Seafood or sea water exposure
    • Travel
    • Occupation
  • Ask about specific symptoms that suggest systemic toxicity to judge the severity of the infection, such as:
    • Severe pain
    • Fever or rigors
    • Palpitations
    • Dizziness
    • Confusion
    • Shortness of breath
  • See table History and Physical Examination Elements for Soft Tissue Infection.
  • See table Risk Factors for Specific Pathogens.
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Use the physical exam to determine the severity and cause of the infection. C

  • Consider the anatomical relationship between different types of skin infection.
  • Consider a diagnosis of soft tissue infection when there is redness of the skin, tenderness, and swelling.
  • Examine skin for inflammatory changes:
    • Lymphangitis, a raised indurate border, a peau d'orange appearance (more indicative of streptococci)
    • Fluctuance, drainage (more indicative of staphylococcal infection)
    • Crepitus (more indicative of anaerobic or gram-negative bacillary infection)
    • Bullae formation, vesicles, induration, and color (to help determine the depth)
  • Examine wounds for a maldorous exudate, as an indication of anaerobic infection.
  • Examine wounds for a sweet exudate, as an indication of Pseudomonas or clostridial infection.
  • Distinguish simple cellulitis from skin changes associated with a deeper infection, such as necrotizing fasciitis or gas gangrene, in patients with:
    • A rapid increase in lesion size
    • Evolution of bullous lesions
    • Reddish-purple coloring of the skin
    • Systemic toxicity
    • Pain out of proportion to the clinical findings
  • Recognize that signs such as confusion, hypotension, tachypnea, tachycardia, and severe tenderness or anesthesia at the site of the infection may represent a life-threatening systemic infection.
  • Recognize a compartment syndrome, characterized by loss of sensation even when peripheral pulses are still palpable.
  • See table History and Physical Examination Elements for Soft Tissue Infection.
  • See figure Anatomical Relationships of Skin and Soft Tissues.
  • See figure Cellulitis.
  • See figure Necrotizing Fasciitis and Myositis (A).
  • See figure Necrotizing Fasciitis and Myositis (B).
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Recognize that underlying comorbid illness can affect the clinical presentation of cellulitis and soft tissue infection. B

  • Recognize that severe infection in dialysis patients may be accompanied by no or low-grade fever.
  • Recognize that in diabetic patients, although fever and leukocytosis may be absent, marked hyperglycemia, with or without ketoacidosis, may suggest a severe infection.
  • Recognize in obese patients deep soft tissue infection can occur with minimal skin changes.
  • Treat immunosuppressed patients with broad spectrum antimicrobials (see Treatment in immunosuppressed patients).
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Use laboratory tests to document infection, judge the severity of illness, determine the cause, and guide initial and definitive antibiotic therapy. C

  • Recognize the need to obtain good diagnostic materials from infected areas for Gram stain, culture, and sensitivites to direct therapy.
  • In patients with signs and symptoms suggesting systemic toxicity, obtain:
    • Blood cultures (two or three sets)
    • CBC and differential
    • Creatinine and BUN
    • CPK
    • Glucose
    • Bicarbonate and other electrolytes
    • Calcium
  • Use plain radiographs, CT, or MRI scans for severe infections when necessary to look for gas in tissue and to determine the extent and severity of infection.
  • See table Laboratory and Other Studies for Soft Tissue Infection.
  • See figure Necrotizing Infections Associated with Gas in the Tissue (A).
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Recognize that soft tissue infections can be caused by a number of different organisms, and are sometimes confused with noninfectious disease processes. C

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FAQs
Dennis L. Stevens, PhD, MD has no financial relationships with pharmaceutical companies, biomedical device manufacturers, or health-care related organizations. Lawrence J. Eron, MD, FACP has no financial relationships with pharmaceutical companies, biomedical device manufacturers, or health-care related organizations.

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