From the Guidelines
Physical exam findings that make cellulitis less likely include bilateral involvement, well-demarcated borders except at the leading edge, lack of warmth or tenderness in the affected area, and absence of lymphangitis or regional lymphadenopathy. The presence of scaling, vesicles, or papules suggests alternative diagnoses like dermatitis or fungal infections 1. If the redness blanches completely with pressure or elevates above the surrounding skin (like in urticaria), cellulitis becomes less probable. Lack of systemic symptoms such as fever or malaise in extensive-appearing inflammation also decreases the likelihood of cellulitis. Additionally, if the erythema follows superficial venous patterns rather than dermatomes or lymphatic drainage, conditions like superficial thrombophlebitis should be considered instead.
Some key points to consider when evaluating a patient for cellulitis include:
- The presence of a wooden-hard feel of the subcutaneous tissues, which is more indicative of fasciitis than cellulitis 1
- The presence of skin discoloration or gangrene, which can be seen in more severe infections 1
- The presence of anesthesia of involved skin, which can be seen in necrotizing fasciitis 1
- The presence of systemic toxicity, such as high temperatures, disorientation, and lethargy, which can indicate a more severe infection 1
It's also important to note that cellulitis is often overdiagnosed, leading to unnecessary antibiotic use. The absence of classic inflammatory signs (dolor, calor, rubor, tumor) in what appears to be a skin infection should prompt consideration of non-infectious mimics like stasis dermatitis, contact dermatitis, or deep vein thrombosis. A recent study published in 2018 provides guidance on the management of skin and soft-tissue infections, including cellulitis, and recommends that treatment should begin promptly with agents effective against the typical Gram-positive pathogens, especially streptococci 1.
From the Research
Physical Exam Findings
The following physical exam findings would make cellulitis less likely:
- Absence of expanding erythema, warmth, tenderness, and swelling 2, 3, 4, 5
- No signs of localized skin erythema, edema, warmth, and tenderness 5
- Lack of systemic illness, such as fever or lymphangitis 6
- Presence of other dermatologic conditions, such as:
- Venous stasis dermatitis 3, 4
- Contact dermatitis 3, 4
- Eczema 3
- Lymphedema 3
- Erythema migrans 3
- Deep vein thrombosis 4
- Panniculitis 4 These conditions can present with similar symptoms to cellulitis, making diagnosis challenging 3, 4. A thorough physical examination and consideration of the patient's history and other diagnostic tests are necessary to rule out cellulitis 2, 3, 4, 5.