CellulitisMANAGEMENT

INFECTIOUS DISEASE PRESENTATIONS · 12 SECTIONS

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490 items

☷ Legend

01Approach to the Critical Patient/attcp39

Immediate priorities

›High-risk states and triggers

›Airway compromise from facial or neck involvement

›Floor of mouth swelling

›Stridor or voice change

›Shock physiology

›SBP < 90 mmHg

›Lactate >= 2 mmol/L

›Rapidly progressive pain out of proportion

›Necrotizing soft tissue infection concern

›Immediate surgical consult

›Immunocompromised host

›Neutropenia

›Solid organ transplant

›Severe systemic toxicity

›Altered mental status

›Rigors

Source control and complications

›Complication screen

›Abscess

›Fluctuance

›Point-of-care ultrasound

›Necrotizing infection

›Crepitus

›Bullae

›Septic arthritis if periarticular erythema

›Pain with passive range of motion

›Joint effusion

›Osteomyelitis if chronicity or ulcer

›Probe-to-bone positive

›Persistent symptoms > 7-14 days

Monitoring and escalation

›Monitoring plan

›Frequent reassessment for progression

›Border marking and time stamp

›Photodocumentation per local policy

›Early IV access if moderate to severe

›Two peripheral IVs if toxicity

›Blood cultures before antibiotics if severe

›Escalation triggers

›Worsening pain

›Expanding erythema despite therapy

02History/hx36

Symptom profile and tempo

›Timeline and pattern

›Onset and progression hours to days

›Rapid progression within 24 hours

›Subacute progression over several days

›Pain severity and character

›Pain out of proportion

›Minimal pain despite erythema

›Systemic symptoms

›Fever or chills

›Malaise

Exposures and portals of entry

›Portal of entry and exposures

›Skin barrier disruption

›Trauma

›Tinea pedis

›Bites and animal exposure

›Cat bite or scratch

›Dog bite

›Water exposure

›Freshwater exposure

›Seawater exposure

›Procedural or injection exposure

›Injection drug use

›Recent surgery

Host factors and recurrence risks

›Risk modifiers

›Prior MRSA colonization or infection

›Recent MRSA abscess

›Household MRSA

›Comorbidities

›Diabetes mellitus

›Chronic edema or lymphedema

›Medication and immune status

›Systemic steroids

›Chemotherapy

›Recurrence history

›Prior cellulitis episodes

›Chronic venous insufficiency

03Physical Exam/exam44

Local exam and mapping

›Local findings

›Erythema, warmth, tenderness

›Border definition

›Lymphangitic streaking

›Purulence assessment

›Fluctuance

›Draining sinus

›Skin integrity

›Fissures between toes

›Ulcers or pressure injuries

Severity and alternative diagnoses

›Severity cues

›Bullae or skin necrosis

›Necrotizing infection concern

›Vascular compromise concern

›Crepitus

›Gas-forming infection concern

›Immediate imaging and surgery consult

›Disproportionate pain

›Necrotizing infection concern

›Immediate surgery consult

›Mimic screen

›Deep vein thrombosis features

›Unilateral swelling disproportionate to erythema

›Calf tenderness without skin break

›Gout or pseudogout features

›Periarticular maximal tenderness

›Limited joint range of motion

›Contact dermatitis features

›Pruritus predominant

›Sharp geometric borders

Regional and systemic exam

›Regional findings

›Lymph nodes

›Tender inguinal or axillary nodes

›Lymphangitis

›Neurovascular status if limb involvement

›Distal pulses

›Sensation and motor function

›Systemic findings

›Fever

›Temperature trend

›Antipyretic masking

›Hemodynamic status

›Tachycardia

›Hypotension

04Differential Diagnosis/ddx39

Life-threatening and can’t-miss

›High-acuity alternatives

›Necrotizing fasciitis

›ICD-10 M72.6

›SNOMED CT necrotizing fasciitis

›Septic arthritis

›ICD-10 M00.x

›SNOMED CT septic arthritis

›Osteomyelitis

›ICD-10 M86.x

›SNOMED CT osteomyelitis

›Compartment syndrome

›ICD-10 T79.Ax

›SNOMED CT compartment syndrome

Mimics and look-alikes

›Noninfectious mimics

›Deep vein thrombosis

›ICD-10 I82.x

›SNOMED CT deep venous thrombosis

›Venous stasis dermatitis

›ICD-10 I87.2

›SNOMED CT stasis dermatitis

›Contact dermatitis

›ICD-10 L23.x

›SNOMED CT allergic contact dermatitis

›Acute gout

›ICD-10 M10.x

›SNOMED CT gout

Etiology patterns by context

›Pathogen and exposure patterns

›Nonpurulent cellulitis

›Beta-hemolytic streptococci typical

›MSSA possible

›Purulent infection

›Staphylococcus aureus typical

›Community-associated MRSA risk dependent

›Animal bites

›Pasteurella species concern

›Polymicrobial including anaerobes

›Water exposure

›Vibrio vulnificus concern with seawater

›Aeromonas concern with freshwater

05Laboratory Tests/lt37

Core labs by severity

›Lab selection framework

›Mild uncomplicated, outpatient candidate

›No routine labs if stable and reliable follow-up

›Glucose if diabetes concern

›Moderate to severe or systemic features

›Complete blood count

›Leukocytosis supports infection

›Normal WBC does not exclude necrotizing infection

›Basic metabolic panel

›Creatinine for antibiotic selection

›Sodium for necrotizing infection risk context

›Lactate

›Lactate >= 2 mmol/L supports hypoperfusion or severe infection

›Lactate >= 4 mmol/L high-risk sepsis physiology

›CRP

›Trend support if admitted

›Non-specific elevation

Cultures and microbiology

›Culture strategy

›Blood cultures

›Severe infection or systemic toxicity

›Immunocompromised host

›Purulent drainage culture

›Abscess drainage specimen

›Recurrent infections

›Skin swabs without purulence

›Low yield

›Avoid routine use

Necrotizing infection adjuncts

›Necrotizing infection supportive labs

›CK

›Myonecrosis concern

›Normal CK does not exclude early disease

›Coagulation panel

›Severe infection or surgery planning

›DIC concern

›Venous blood gas if critically ill

›pH trend

›CO2 in mmHg when reported

06Diagnostic Tests/dt42

Scoring Systems

›Risk stratification tools

›LRINEC score for necrotizing infection

›Use as adjunct only

›Low sensitivity in early disease

›qSOFA for sepsis risk

›RR >= 22 per minute

›SBP <= 100 mmHg

›Altered mental status

›Clinical severity grouping for cellulitis

›Mild

›Moderate

›Severe

MRI

›MRI use cases

›Osteomyelitis evaluation

›High sensitivity for marrow edema

›Useful for diabetic foot extension

›Deep soft tissue infection extent

›Fascia involvement concern

›Surgical planning support

›Limitations

›Time and availability constraints

›Metal implants and contraindications

›CT use cases

›Suspected necrotizing infection

›Fascial thickening

›Gas in soft tissues

›Deep abscess detection

›Perineal or pelvic source concern

›Facial or orbital extension concern

›Contrast considerations

›Creatinine and contrast risk context

›Alternative imaging if severe CKD

Ultrasound (or US)

›Ultrasound roles

›Abscess vs cellulitis

›Cobblestoning supports cellulitis

›Anechoic or complex collection supports abscess

›Foreign body

›Radiolucent material detection

›Guided removal planning

›DVT evaluation adjunct

›Compression ultrasound if clinical suspicion

›Alternative diagnosis consideration

07Disposition/dispo37

Admission and level of care

›Admission indications

›Systemic toxicity

›Persistent fever

›Hemodynamic instability

›Rapid progression

›Expanding erythema despite initial therapy

›Severe pain

›High-risk anatomy

›Periorbital

›Hand involvement with functional compromise

›Unable to tolerate oral therapy

›Vomiting

›Malabsorption concern

›High-risk host

›Immunocompromised

›Poorly controlled diabetes

›Higher level of care triggers

›Sepsis with lactate >= 2 mmol/L and hypotension

›Vasopressor need

›ICU consideration

›Necrotizing infection concern

›Immediate surgery

›Broad-spectrum IV antibiotics

Discharge criteria and follow-up

›Outpatient criteria

›No systemic toxicity

›Stable vitals

›Reliable oral intake

›No necrotizing infection concern

›No pain out of proportion

›No crepitus or bullae

›Reliable follow-up

›Recheck in 24-48 hours if progression risk

›Return precautions understood

›Follow-up plan

›Border marking for self-monitoring

›Daily photo optional

›Measure spread beyond line

08Treatment/t107

General management

›Core principles

›Purulent source control

›Incision and drainage for abscess

›Culture of drainage when feasible

›Nonpurulent cellulitis therapy

›Streptococcal coverage primary

›MRSA coverage based on risk and purulence

›Supportive care

›Elevation of affected limb

›Analgesia

Oral antibiotics for outpatient

›Nonpurulent, mild to moderate

›Cephalexin

›Adults 500 mg PO q6h

›Typical duration 5 days

›Extend 7-10 days if slow response

›Pediatrics 25-50 mg/kg/day PO divided q6-8h

›Max 4 g/day

›Duration 5-7 days

›Dicloxacillin

›Adults 500 mg PO q6h

›Duration 5 days

›Extend if slow response

›Purulent or MRSA risk

›Trimethoprim-sulfamethoxazole

›Adults 1-2 DS tablets PO BID

›Add beta-lactam if nonpurulent component

›Duration 5-10 days based on response

›Pediatrics 8-12 mg/kg/day TMP component PO divided BID

›Max 320 mg TMP/day typical

›Avoid in infants < 2 months

›Doxycycline

›Adults 100 mg PO BID

›Add beta-lactam for streptococcal coverage if nonpurulent

›Avoid in pregnancy

›Pediatrics >= 8 years 2.2 mg/kg/dose PO BID

›Max 100 mg/dose

›Duration 5-10 days

›Clindamycin

›Adults 300-450 mg PO q6-8h

›C difficile risk counseling

›Duration 5-10 days

›Pediatrics 20-40 mg/kg/day PO divided q6-8h

›Max 1.8 g/day typical

›Duration 5-10 days

IV antibiotics for inpatient or severe

›Nonpurulent, moderate to severe

›Cefazolin

›Adults 2 g IV q8h

›Adjust for renal dysfunction

›Step-down to cephalexin when improving

›Pediatrics 25-50 mg/kg/dose IV q8h

›Max 2 g/dose

›Step-down when stable

›Ceftriaxone

›Adults 1-2 g IV q24h

›Useful for outpatient parenteral therapy

›Step-down when improving

›Pediatrics 50 mg/kg IV q24h

›Max 2 g/day

›Step-down when improving

›MRSA coverage when indicated

›Vancomycin

›Adults 15-20 mg/kg IV q8-12h

›AUC-guided monitoring when available

›Adjust to renal function and levels

›Pediatrics 15 mg/kg IV q6h

›Trough or AUC monitoring per local protocol

›Adjust to renal function

›Linezolid

›Adults 600 mg IV q12h

›Serotonergic interaction risk

›Thrombocytopenia monitoring

›Pediatrics < 12 years 10 mg/kg IV q8h

›Pediatrics >= 12 years 600 mg IV q12h

›CBC monitoring

Necrotizing infection or polymicrobial risk

›Broad-spectrum regimens

›Vancomycin plus piperacillin-tazobactam

›Vancomycin dosing per weight and renal function

›Initial 15-20 mg/kg IV

›Maintenance q8-12h with monitoring

›Piperacillin-tazobactam 4.5 g IV q6-8h

›Renal adjustment required

›Add clindamycin for toxin suppression if GAS suspected

›Vancomycin plus cefepime plus metronidazole

›Cefepime 2 g IV q8-12h

›Renal adjustment required

›Neurotoxicity risk in renal dysfunction

›Metronidazole 500 mg IV q8h

›Anaerobe coverage

›Avoid alcohol exposure

›Clindamycin 900 mg IV q8h if toxin-mediated concern

›Streptococcal toxic shock concern

›Necrotizing infection adjunct

Adjuncts and supportive therapy

›Symptom control

›Acetaminophen

›Adults 650-1000 mg PO or PR q6-8h

›Max 4 g/day

›Lower max in chronic liver disease

›Pediatrics 15 mg/kg PO q4-6h

›Max 75 mg/kg/day

›Max 4 g/day absolute

›NSAID use

›Avoid if AKI risk or severe infection with hypoperfusion

›Caution in older adults

›Edema management

›Limb elevation

›Above heart level when feasible

›Compression after acute phase if chronic edema

09Special Populations/sp30

Pregnancy

›Pregnancy considerations

›Antibiotic selection

›Beta-lactams preferred when appropriate

›Avoid doxycycline

›MRSA options

›Clindamycin if susceptible

›Vancomycin for severe infection

›Disposition threshold

›Lower threshold for IV therapy if systemic toxicity

›OB consultation if abdominal or pelvic involvement

Geriatric

›Older adult considerations

›Atypical presentation

›Afebrile infection common

›Delirium as toxicity marker

›Medication risks

›Renal dosing adjustments common

›Drug-drug interactions and polypharmacy

›Complication risk

›Higher bacteremia risk with severe disease

›Lower threshold for admission if frail

Pediatrics

›Pediatric considerations

›Common portals

›Impetigo

›Insect bites

›Weight-based dosing

›Cephalexin dosing by kg

›Clindamycin dosing by kg

›Periorbital involvement

›Orbital cellulitis red flags

›CT orbit if proptosis or ophthalmoplegia

10Background/b38

Epidemiology

›Disease burden and patterns

›Common skin and soft tissue infection presentation in acute care

›Lower extremity predominance

›Recurrence common with chronic edema

›Typical microbiology

›Beta-hemolytic streptococci common in nonpurulent cellulitis

›Staphylococcus aureus common in purulent infection

›Coding and terminology

›ICD-10 L03.0 cellulitis of finger and toe

›ICD-10 L03.1 cellulitis of other parts of limb

›ICD-10 L03.2 cellulitis of face

›ICD-10 L03.3 cellulitis of trunk

›ICD-10 L03.9 cellulitis, unspecified

›SNOMED CT cellulitis

›SNOMED CT erysipelas

Pathophysiology

›Mechanism overview

›Dermis and subcutaneous tissue infection

›Barrier disruption enables bacterial entry

›Local inflammatory response drives erythema and warmth

›Lymphatic involvement

›Lymphangitis and tender nodes

›Post-inflammatory lymphedema contributes to recurrence

›Progression pathways

›Abscess formation with purulent pathogens

›Deep extension to fascia in necrotizing infection

Therapeutic Considerations

›Treatment rationale

›Nonpurulent cellulitis

›Streptococcal coverage primary

›MRSA coverage selective based on risk

›Purulent infections

›Incision and drainage key intervention

›Antibiotics adjunct based on severity and host risk

›Duration strategy

›5-day courses effective for many uncomplicated cases

›Extension if slow clinical response

›Response expectations

›Early worsening within 24 hours possible from inflammation

›Clinical improvement expected by 48-72 hours

11Patient Discharge Instructions/pdi24

copy discharge instructions

›Discharge instructions

›Antibiotic adherence

›Take exactly as prescribed

›Do not stop early if improving

›Local care

›Elevation as much as possible for 48-72 hours

›Keep skin clean and dry

›Monitoring

›Expect gradual improvement over 2-3 days

›Border marking to track spread

›Return to ED immediately

›Rapidly spreading redness beyond marked border

›Severe pain or pain out of proportion

›Fever or shaking chills

›New blistering, black skin, or crepitus

›Dizziness, fainting, confusion

›Inability to keep fluids or medications down

›Follow-up

›Recheck in 24-48 hours if not clearly improving

›Earlier recheck for diabetes, immunocompromise, or facial involvement

›Prevention of recurrence

›Treat athlete’s foot if present

›Moisturize cracked skin and address fissures

›Compression after acute phase if chronic edema and cleared by clinician

12References/r17

Clinical guidelines and evidence sources

›Guideline sources

›Infectious Diseases Society of America skin and soft tissue infection guideline

›Nonpurulent cellulitis management framework

›Purulent infection and abscess management framework

›Sepsis consensus recommendations

›Lactate use for risk stratification

›Early antibiotics in suspected sepsis

›Antimicrobial stewardship principles

›Narrow therapy when appropriate

›Shorter effective durations when improving

›Decision support and reviews

›Necrotizing soft tissue infection diagnostic limitations

›LRINEC limitations in early disease

›Clinical judgment and surgical exploration priority when suspected

›MRSA therapy considerations

›Local antibiogram guidance

›Clindamycin inducible resistance consideration

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Reviewed by SymptomDx Medical Team · Last reviewed June 16, 2026

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