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Are You Sure It’s Cellulitis?

Greg Moran, MD, Matthew DeLaney, MD, FACEP, FAAEM, and Mizuho Morrison, DO

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Many times patients who present with an inflamed lower extremity are diagnosed with cellulitis. However before we jump to this diagnosis, it’s important to stop and consider other diagnosis. Greg Moran, EM/IM and infectious disease expert shares his insights and reviews recent treatment recommendations.


  • Cephalexin alone is the treatment of choice for patients with uncomplicated, non-purulent cellulitis

  • Avoid the use of a one time dose IV/ IM antibiotics in the UC



  • Chronic venous stasis can be difficult to distinguish from cellulitis as it also causes pain,  edema, and dependent erythema

  • Patients with chronic venous stasis and lymphedema are at increased risk for cellulitis and superinfection

  • Weng QY,  et al. Costs and Consequences Associated With Misdiagnosed Lower Extremity Cellulitis. JAMA Dermatol. 2016 [PMID: 27806170]

    • Of 259 patients admitted through the emergency department with a cellulitis, ⅓ were found by a panel of dermatologists to simply have an exacerbation of an underlying skin condition

  • Consider an alternative diagnosis when evaluating a patient with what looks like bilateral cellulitis as this is less likely to be secondary to infection



  • Determining the baseline appearance of the legs will help differentiate chronic stasis dermatitis from a superimposed cellulitis

  • Minor skin changes over a long period of time are less concerning cellulitis while rapid involvement is more likely infectious

  • Fever suggests infection, but absence of fever does not rule out cellulitis

  • Consider DVT if high risk for thrombosis as DVT can also cause erythema and swelling



  • Cellulitis without abscess is most likely secondary to streptococcal infection.

  • Cephalexin monotherapy will cover both streptococcus and MSSA and is the treatment of choice for outpatient management of uncomplicated cellulitis.

  • For cellulitis with abscess the addition of  trimethoprim-sulfamethoxazole (Bactrim) is recommended if there is concern for MRSA.

  • Moran GJ, et al. Effect of Cephalexin Plus Trimethoprim-Sulfamethoxazole vs Cephalexin Alone on Clinical Cure of Uncomplicated Cellulitis: A Randomized Clinical Trial. JAMA. 2017;317(20):2088-2096 [PMID: 28535235]

    • In this multicenter, double-blind, randomized superiority trial of roughly 500  patients with uncomplicated cellulitis, the use of cephalexin plus trimethoprim-sulfamethoxazole compared to cephalexin alone did not result in higher rates of clinical resolution of cellulitis.

  • Give the first dose of oral antibiotic in the urgent care before discharging the patient instead of a one time dose of IM or IV antibiotic.

  • There are no good clinical decision rules or clinical criteria to help risk-stratify patients who can be treated safely as an outpatient compared to those that need admission to the hospital.

  • Talan DA, et al. Factors associated with decision to hospitalize emergency department patients with skin and soft tissue infection. West J Emerg Med. 2015;16(1):89-97 [PMID: 25671016]

    • Among roughly 600 patients who presented to the ER for skin and soft tissue infections, 15% were admitted, ~40% of which were admitted only for IV antibiotics.

  • Demarking the patient’s cellulitis with a pen along the outer edges will help the patient track their progress and assist physician decision-making should the patient bounce back to the hospital.

  • Patients should be given clear discharge instructions to return to the hospital should their cellulitis progress.

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Will You Be My Facebook Friend? Full episode audio for MD edition 184:48 min - 87 MB - M4AHippo Primary Care RAP - Apirl 2018 Written Summary 399 KB - PDF