eMedicine Specialties > Infectious Diseases > Skin and Soft-Tissue Infections

Cellulitis: Differential Diagnoses & Workup

Author: Isaac P Humphrey, MD, Assistant Professor of Internal Medicine, Uniformed Services University of the Health Sciences; Clinical Instructor of Internal Medicine, Wright State University Boonshoft School of Medicine
Coauthor(s): Eric S Halsey, MD, Chief, Department of Infectious Diseases, Wright-Patterson Air Force Base; Assistant Professor of Medicine, Uniformed Services University of the Health Sciences; Assistant Professor of Medicine, Wright State University
Contributor Information and Disclosures

Updated: Sep 23, 2009

Differential Diagnoses

Burn Wound Infections
Pyoderma Gangrenosum
Carcinoma erysipelatoides
Sarcoidosis
Contact Dermatitis, Allergic
Septic Arthritis
Deep Venous Thrombosis
Stinging Insect Hypersensitivity
Fixed Drug Eruptions
Superficial Thrombophlebitis
Gout
Toxic Shock Syndrome
Leukemia
Urticaria
Lymphoma
Wells Syndrome (Eosinophilic Cellulitis)
Mycosis Fungoides
Paget Disease
Panniculitis

Workup

Laboratory Studies

Laboratory studies are unnecessary in most patients with cellulitis. The following laboratory tests may be considered in patients who present with moderate to severe cellulitis and/or systemic symptoms:

  • Complete blood count (CBC) often shows leukocytosis in the setting of severe disease. Leukopenia may also be present in severe disease, especially in cases of toxin-mediated cellulitis.
  • In most cases of cellulitis, blood cultures are neither necessary nor cost-effective. However, they should be obtained in patients who are admitted for moderate to severe disease.14
  • Gram stain, whether obtained via biopsy or aspiration of the infected area, is low-yield and unnecessary in most cases unless purulent material is draining or bullae or abscess is present.
  • Baseline creatinine studies may be helpful to assess baseline renal function in order to correctly prescribe antimicrobials.

Imaging Studies

As with laboratory studies, most cases of cellulitis do not require imaging. However, consider imaging in the following clinical scenarios:

  • Current data suggest that ultrasonography may play a role in the detection of occult abscess and direction of care, especially in an emergency department setting.15
  • If necrotizing fasciitis is a concern, MRI may help to rule this out.16 However, strong clinical suspicion of this disease should prompt surgical consultation without delay for imaging.

Procedures

In routine cases of cellulitis, additional procedures are unnecessary. However, in more severe disease or unique clinical scenarios, additional procedures may be indicated.

  • Aspiration or punch biopsy of the inflamed area may have a culture yield of 2%-40% and is of limited clinical value in most cases.17
  • Incision and drainage of an abscess with Gram stain and culture yields positive culture results in more than 90% of cases.14
  • Dissection to the underlying fascia to assess for necrotizing fasciitis is indicated upon clinical concern following initial evaluation and imaging studies.18

Histologic Findings

Tissue stains and microscopy reveal WBC infiltration, usually neutrophil predominance, bacteria, and cellular debris. Biopsy is not routine but may be performed in an attempt to rule out a noninfectious entity.

More on Cellulitis

Overview: Cellulitis
Differential Diagnoses & Workup: Cellulitis
Treatment & Medication: Cellulitis
Follow-up: Cellulitis
Multimedia: Cellulitis
References
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References

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Further Reading

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Keywords

cellulitis, gram-positive bacteria, group A beta-hemolytic Streptococcus, GABHS, Staphylococcus aureus, S aureus, MRSA, methicillin-resistant Staphylococcus aureus, CA-MRSA, community-acquired MRSA, Streptococcus pyogenes, S pyogenes, systemic toxins, bacteremia, sepsis, buccal cellulitis, Haemophilus influenzae type B, HIB, facial cellulitis, perianal cellulitis, group B Streptococcus cellulitis, Pseudomonas osteomyelitis, septic arthritis, thrombophlebitis, Pasteurella multocida, P multocida, Vibrio vulnificus, V vulnificus, Aeromonas species, Clostridium perfringens, C perfringens, crepitus, crepitation, Escherichia coli cellulitis, E coli, septic shock

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Contributor Information and Disclosures

Author

Isaac P Humphrey, MD, Assistant Professor of Internal Medicine, Uniformed Services University of the Health Sciences; Clinical Instructor of Internal Medicine, Wright State University Boonshoft School of Medicine
Isaac P Humphrey, MD is a member of the following medical societies: American College of Physicians and American Medical Association
Disclosure: Nothing to disclose.

Coauthor(s)

Eric S Halsey, MD, Chief, Department of Infectious Diseases, Wright-Patterson Air Force Base; Assistant Professor of Medicine, Uniformed Services University of the Health Sciences; Assistant Professor of Medicine, Wright State University
Eric S Halsey, MD is a member of the following medical societies: American College of Physicians, Armed Forces Infectious Diseases Society, HIV Medicine Association of America, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

Medical Editor

Fred A Lopez, MD, Associate Professor and Vice Chair, Department of Medicine, Assistant Dean for Student Affairs, Louisiana State University School of Medicine
Fred A Lopez, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians-American Society of Internal Medicine, Infectious Diseases Society of America, and Louisiana State Medical Society
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

Charles V Sanders, MD, Edgar Hull Professor and Chairman, Department of Internal Medicine, Professor of Microbiology, Immunology and Parasitology, Louisiana State University School of Medicine at New Orleans; Medical Director, Medicine Hospital Center, Charity Hospital and Medical Center of Louisiana at New Orleans; Consulting Staff, Ochsner Medical Center
Charles V Sanders, MD is a member of the following medical societies: Alliance for the Prudent Use of Antibiotics, Alpha Omega Alpha, American Association for the Advancement of Science, American Association of University Professors, American Clinical and Climatological Association, American College of Physician Executives, American College of Physicians, American Federation for Medical Research, American Foundation for AIDS Research, American Geriatrics Society, American Lung Association, American Medical Association, American Society for Microbiology, American Thoracic Society, American Venereal Disease Association, Association for Professionals in Infection Control and Epidemiology, Association of American Medical Colleges, Association of American Physicians, Association of Professors of Medicine, Infectious Disease Society for Obstetrics and Gynecology, Infectious Diseases Society of America, Louisiana State Medical Society, Orleans Parish Medical Society, Royal Society of Medicine, Sigma Xi, Society of General Internal Medicine, Southeastern Clinical Club, Southern Medical Association, Southern Society for Clinical Investigation, and Southwestern Association of Clinical Microbiology
Disclosure: Nothing to disclose.

CME Editor

Eleftherios Mylonakis, MD, Clinical and Research Fellow, Department of Internal Medicine, Division of Infectious Diseases, Massachusetts General Hospital
Eleftherios Mylonakis, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Physicians, American Society for Microbiology, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

Chief Editor

Burke A Cunha, MD, Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital
Burke A Cunha, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

 
 
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