This episode will help you recognize cellulitis and even differentiate it from erysipelas which is totally a different thing. You’ll also learn about treatment, whether or not a blood culture is necessary, and a whole lot more.

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References

Chen AE, Carroll KC, Diener-West M, Ross T, Ordun J, Goldstein MA, Kulkarni G, Cantey JB, Siberry GK. Randomized controlled trial of cephalexin versus clindamycin for uncomplicated pediatric skin infections. Pediatrics. 2011 Mar;127(3):e573-80. doi: 10.1542/peds.2010-2053. Epub 2011 Feb 21. PMID: 21339275; PMCID: PMC3387913.

Daniel J. Pallin, William D. Binder, Matthew B. Allen, Molly Lederman, Siddharth Parmar, Michael R. Filbin, David C. Hooper, Carlos A. Camargo, Clinical Trial: Comparative Effectiveness of Cephalexin Plus Trimethoprim-Sulfamethoxazole Versus Cephalexin Alone for Treatment of Uncomplicated Cellulitis: A Randomized Controlled Trial, Clinical Infectious Diseases, Volume 56, Issue 12, 15 June 2013, Pages 1754–1762, https://doi.org/10.1093/cid/cit122

Liu C, Bayer A, Cosgrove SE, et al. Clinical practice guidelines by the infectious diseases society of america for the treatment of methicillin-resistant Staphylococcus aureus infections in adults and children. Clin Infect Dis 2011; 52:e18.

Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the Infectious Diseases Society of America. Clin Infect Dis 2014; 59:e10.

Transcript

Note: This transcript was partially completed with the use of the Descript AI

 Welcome to another episode of PEM Currents, the Pediatric Emergency Medicine Podcast. As always, I’m your host, Brad Sobolewski, and today’s episode is all about cellulitis. What is it? Well when a break in the skin occurs, normal skin, flora, and bacteria can enter the subcutaneous tissue, where they do not belong, and they can also invade the lymphatic system.

And although this podcast episode is entitled cellulitis, I’m also going to talk about erysipelas. The two terms are not interchangeable. but both manifest as areas of skin, erythema, edema, and warmth. Cellulitis involves the deeper dermis and subcutaneous fat. Whereas erysipelas involves the upper dermis and there’s a more clear demarcation between the involved and uninvolved tissue.

There’s a fun fact, since the ear doesn’t have deep or dermal tissue, it’s always. ear-a-sipelas. I’ll pause for laughter. Anyway, a skin abscess, which is not the focus of this episode, is a collection of pus deep within the dermis or subcutaneous space. Impetigo, also not included in this episode, is a very superficial infection with that honey crusted drainage. There are also bullous versions. So cellulitis tends to develop in a bit more of an indolent fashion over a few to several days, whereas erys syphilis is more acute. You get systemic symptoms faster, such as fever. Chills, severe malaise, and headache. These can precede the onset of the local skin changes and start just in a matter of hours.

Clinically, for both, you’ll see areas of skin erythema. edema and warmth. You can also see petechiae and hemorrhage, as well as superficial bulla, vesicles, or even echemosis. Sometimes you also see regional lymphangitis or enlargement of the regional lymph nodes. If you’ve got a lot of edema surrounding the hair follicles, you can see some dimpling in the skin.

This creates an orange peel texture appearance, peau d’orange. I hope I pronounced that right. I took Spanish in high school. Anyway, the skin is warm to the touch, it’s uncomfortable, it hurts with movement, and some patients can describe an itchiness or a tight feeling in addition to the pain. You may see fever and other systemic symptoms, and cellulitis and erysipelas, especially in children, are nearly Always unilateral.

Bilateral red limbs? That’s probably something different. Complications that you should be aware of include bacteremia, endocarditis, septic arthritis, or osteomyelitis. Full blown sepsis and toxic shock syndrome. Fortunately, those are rare. So, in general, mild cellulitis has no systemic features in a patient with no significant comorbidities.

Moderate cellulitis has moderate swelling and tenderness with some systemic features like fever or tachycardia. Severe cellulitis has severe swelling and tenderness. really affecting function. It’s a larger body surface area, and you’ve got marked systemic features. So fever or hypothermia, extreme tachycardia, tachypnea, altered consciousness, a very unwell appearance, or even hypotension.

So what causes it? Well, bacteria, and the most common etiology. Staphylococcus aureus is actually an infrequent cause of cellulitis in children. But it can be seen more often in penetrating wounds. Methicillin resistant Staphylococcus aureus classically causes abscess formation. So you won’t really see that as the cause of isolated cellulitis or erysiplas in children.

So how do you make the diagnosis? Well, it’s clinical, right? Look for areas of skin that are erythematous, edematous, warm, and painful. Labs or imaging are not routinely necessary. If you think that there’s an abscess, you can diagnose it clinically by a localized area of induration or fluctuance or use an ultrasound.

Cellulitis can look like a cobblestone street on sonogram. And you should consider whether or not an abscess is present if you see significant induration, so thickening or hardening of the soft tissues, of greater than three centimeters or non uniform induration. The lesion’s been present greater than two to three days and changing or getting worse, and there’s a history of a previous incision and drainage in that patient.

And so do you need labs? Nah, not really. And the vast majority of patients of CBC or other labs will not aid in making the diagnosis of cellulitis. What about blood culture? Every febrile kid with cellulitis needs a blood culture, right? Not so fast, right? A blood culture can cost more than $200-300.

If you’re sending the kid home. Well, you definitely shouldn’t be sending a blood culture because if you’re worried about bacteremia and sepsis, that kid needs to stay in the hospital. And think about the risk of a false positive versus the risk of a true positive. So if the risk of a contaminant culture is greater than the risk of actually catching a bacteria, then don’t send it.

The cost of false positive cultures, repeat visits, length of stay, could be in the thousands of dollars. And so a lot of the previous studies on getting blood cultures were done in the immediate post Haemophilus influenzae B and Prevnar vaccine era. And we do now live in an era where these invasive organisms are fortunately not as big of a concern.

Vaccinate your children, people. But we do deal with MRSA. But still, for mild and moderate cellulitis, MRSA’s not really the etiology. And so even if a kid has a fever, But they look better after a dose of acetaminophen or ibuprofen. You don’t routinely need a blood culture. Now you could even admit a kid for IV antibiotics, maybe they’re dehydrated or they can’t take PO for some reason, without sending a blood culture.

So, admission does not mandate a blood culture. As always, you want to check with your local recommendations and follow algorithms present at your institution. So, what about disposition? So, with prompt identification and t