Cellulitis, when you think about it, is probably not the most helpful term. Literally, it means “infection of cells.” What cells? The anatomical area is actually the dermis, as well as the subcutaneous tissue.
A patient presenting with “dermitis” has a lesion that is clearly confined to the skin. A patient presenting with significant edema has involvement of subcutaneous tissues. These are the patients where we need to consider the surgical diseases: necrotizing fasciitis, pyomyositis, and abscess.
There is very little in the literature about palpation of the erythematous lesion. However, extensive induration might be the trigger that leads you to perform an ultrasound, and find an abscess.
The other traditional role for palpation is with erysipelas. This streptococcal infection is most commonly encountered in the lower extremities. Traditionally it was thought of as confined to the epidermis, palpable, with sharp borders. But now it is believed that erysipelas and cellulitis are the same disease, on a spectrum depending on how superficial the infection is.[Kilburn Cochrane Database Syst Rev. 2010]
Palpation in cellulitis probably does not receive enough attention in the medical literature. The next time you have a patient with cellulitis, pay particular attention to palpation. It may signal to you that there is something deeper to find on ultrasound.
Take home points:
Erythema of the skin sometimes hides something below
Use palpation to better understand where the inflammation is located