Editing Cellulitis (section)

==Diagnosis==
Cellulitis is most often a clinical diagnosis, readily identified in many people by history and physical examination alone, with rapidly spreading areas of cutaneous [[edema|swelling]], redness, and heat, occasionally associated with inflammation of regional lymph nodes. While classically distinguished as a separate entity from erysipelas by spreading more deeply to involve the subcutaneous tissues, many clinicians may classify erysipelas as cellulitis.  Both are often treated similarly, but cellulitis associated with [[Boil|furuncles]], [[carbuncle]]s, or [[abscess]]es is usually caused by ''[[Staphylococcus aureus|S. aureus]]'', which may affect treatment decisions, especially antibiotic selection.<ref name=":0">{{cite journal |last1=Stevens |first1=Dennis L. |last2=Bisno |first2=Alan L. |last3=Chambers |first3=Henry F. |last4=Dellinger |first4=E. Patchen |last5=Goldstein |first5=Ellie J. C. |last6=Gorbach |first6=Sherwood L. |last7=Hirschmann |first7=Jan V. |last8=Kaplan |first8=Sheldon L. |last9=Montoya |first9=Jose G. |last10=Wade |first10=James C. |title=Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the infectious diseases society of America |journal=Clinical Infectious Diseases|date=15 July 2014 |volume=59 |issue=2 |pages=147–159 |doi=10.1093/cid/ciu296 |pmid=24947530 |doi-access= }}</ref> Skin aspiration of nonpurulent cellulitis, usually caused by streptococcal organisms, is rarely helpful for diagnosis, and [[blood culture]]s are positive in fewer than 5% of all cases.<ref name=":0" />

It is important to evaluate for co-existent abscess, as this finding usually requires surgical drainage as opposed to antibiotic therapy alone.  Physicians' clinical assessment for abscess may be limited, especially in cases with extensive overlying induration, but use of [[Medical ultrasound|bedside ultrasonography]] performed by an experienced practitioner readily discriminates between abscess and cellulitis and may change management in up to 56% of cases.<ref name=":1">{{cite journal |last1=Singer |first1=Adam J. |last2=Talan |first2=David A. |title=Management of skin abscesses in the era of methicillin-resistant Staphylococcus aureus |journal=The New England Journal of Medicine |date=13 March 2014 |volume=370 |issue=11 |pages=1039–1047 |doi=10.1056/NEJMra1212788 |pmid=24620867 }}</ref> Use of ultrasound for abscess identification may also be indicated in cases of antibiotic failure.  Cellulitis has a characteristic "cobblestoned" appearance indicative of subcutaneous edema without a defined hypoechoic, heterogeneous fluid collection that would indicate abscess.<ref>{{cite book |last1=Mayeaux |first1=E. J. |title=The Essential Guide to Primary Care Procedures |date=2015 |publisher=Lippincott Williams & Wilkins |isbn=978-1-4963-1871-8 }}{{page needed|date=November 2022}}</ref>

===Differential diagnosis===
Other conditions that may mimic cellulitis include [[Venous thrombosis|deep vein thrombosis]], which can be diagnosed with a compression leg [[medical ultrasonography|ultrasound]], and [[stasis dermatitis]], which is inflammation of the skin from poor blood flow. Signs of a more severe infection such as necrotizing fasciitis or [[gas gangrene]] that would require prompt surgical intervention include purple [[bulla (dermatology)|bulla]]e, skin sloughing, subcutaneous edema, and systemic toxicity.<ref name=":0" /> Misdiagnosis can occur in up to 30% of people with suspected lower-extremity cellulitis, leading to 50,000 to 130,000 unnecessary hospitalizations and $195 to $515 million in avoidable healthcare spending annually in the United States.<ref>{{Cite journal |last1=Weng |first1=Qing Yu |last2=Raff |first2=Adam B. |last3=Cohen |first3=Jeffrey M. |last4=Gunasekera |first4=Nicole |last5=Okhovat |first5=Jean-Phillip |last6=Vedak |first6=Priyanka |last7=Joyce |first7=Cara |last8=Kroshinsky |first8=Daniela |last9=Mostaghimi |first9=Arash |title=Costs and Consequences Associated With Misdiagnosed Lower Extremity Cellulitis |journal=JAMA Dermatology |volume=153 |issue=2 |pages=141–146 |doi=10.1001/jamadermatol.2016.3816 |pmid=27806170 |year=2017 |s2cid=205110504 |url=https://dash.harvard.edu/bitstream/1/33785925/1/jamadermatology_Weng_2016_oi_160057.pdf }}</ref> Evaluation by dermatologists for cases of suspected cellulitis has been shown to reduce misdiagnosis rates and improve patient outcomes.<ref name="pmid29453874">{{cite journal |vauthors = Li DG, Xia FD, Khosravi H, Dewan AK, Pallin DJ, Baugh CW | display-authors=etal |title=Outcomes of Early Dermatology Consultation for Inpatients Diagnosed With Cellulitis. |journal=JAMA Dermatol |year=2018 |volume=154 |issue=5 |pages=537–543 |pmid=29453874 |doi=10.1001/jamadermatol.2017.6197 |pmc=5876861}}</ref><ref name="pmid29453872">{{cite journal |vauthors = Ko LN, Garza-Mayers AC, St John J, Strazzula L, Vedak P, Shah R | display-authors=etal |title=Effect of Dermatology Consultation on Outcomes for Patients With Presumed Cellulitis: A Randomized Clinical Trial. |journal=JAMA Dermatol |year=2018 |volume=154 |issue=5 |pages=529–536 |pmid=29453872 |doi=10.1001/jamadermatol.2017.6196 |pmc=5876891}}</ref>

Associated musculoskeletal findings are sometimes reported. When it occurs with [[acne conglobata]], [[hidradenitis suppurativa]], and [[pilonidal cyst]]s, the syndrome is referred to as the [[follicular occlusion triad]] or tetrad.<ref>{{cite journal |vauthors=Scheinfeld NS |title=A case of dissecting cellulitis and a review of the literature |journal=Dermatology Online Journal |volume=9 |issue=1 |pages=8 |date=February 2003 |doi=10.5070/D39D26366C |pmid=12639466 }}</ref>

[[Lyme disease]] can be misdiagnosed as cellulitis. The characteristic [[Erythema chronicum migrans|bullseye rash]] does not always appear in Lyme disease (the rash may not have a central or ring-like clearing, or not appear at all).<ref name=wright_2012>{{cite journal |last1=Wright |first1=William F. |last2=Riedel |first2=David J. |last3=Talwani |first3=Rohit |last4=Gilliam |first4=Bruce L. |title=Diagnosis and management of Lyme disease |journal=American Family Physician |date=1 June 2012 |volume=85 |issue=11 |pages=1086–1093 |pmid=22962880 |url=https://www.aafp.org/link_out?pmid=22962880 }}</ref> Factors supportive of Lyme include recent outdoor activities where Lyme is common and rash at an unusual site for cellulitis, such as [[armpit]], [[groin]], or behind the knee.<ref name=CDC-Lyme-Data>{{cite web |title=Lyme Disease Data and surveillance |url=https://www.cdc.gov/lyme/datasurveillance/ |website=Lyme Disease |publisher=Centers for Disease Control and Prevention |access-date=April 12, 2019 |date=2019-02-05 |archive-date=2019-04-13 |archive-url=https://web.archive.org/web/20190413133319/https://www.cdc.gov/lyme/datasurveillance/ |url-status=live }}</ref><ref name=wright_2012/> Lyme can also result in long-term neurologic complications.<ref name=Aucott2015>{{cite journal |vauthors=Aucott JN |title=Posttreatment Lyme disease syndrome |journal=Infectious Disease Clinics of North America |volume=29 |issue=2 |pages=309–323 |date=June 2015 |pmid=25999226 |doi=10.1016/j.idc.2015.02.012}}</ref> The standard treatment for cellulitis, [[cephalexin]], is not useful in Lyme disease.<ref name=IDSALyme2006/> When it is unclear which one is present, the [[Infectious Diseases Society of America|IDSA]] recommends treatment with [[cefuroxime axetil]] or [[amoxicillin/clavulanic acid]], as these are effective against both infections.<ref name=IDSALyme2006/>