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History
Presenting features
Symptom profile
Location
Number of lesions
Size change over time
Drainage
Color change
Pruritus
Pain
Fever
Chills
Systemic symptoms
OPQRST
Onset
Time of onset
Rapid progression
Gradual progression
Provocation and palliation
Worse with pressure
Worse with movement
Improved with elevation
Improved with analgesics
Quality
Throbbing
Sharp
Burning
Pressure
Region and radiation
Localized
Tracking pain
Joint region involvement
Severity
Pain scale 0 to 10
Functional limitation
Timing
Constant
Intermittent
Night worsening
Associated symptoms
Nausea
Vomiting
Malaise
Headache
Myalgias
Lymph node pain
New rash
Urinary symptoms
Respiratory symptoms
Exposure and context
Trauma
Insect bite
Shaving
Tattoo
Skin picking
Recent water exposure
Animal bite
Human bite
Prior episodes
Similar lesion history
Prior incision and drainage
Prior MRSA history
Prior antibiotic failures
Alarm Features
Immediate escalation triggers
Sepsis and shock concern
SBP less than 90 mmHg
MAP less than 65 mmHg
Lactate elevated
Altered mental status
Respiratory distress
Necrotizing soft tissue infection concern
Pain out of proportion
Rapid progression hours
Crepitus
Skin necrosis
Bullae
Anesthesia over skin
Toxic appearance
Deep space and critical location concern
Periorbital involvement
Facial triangle involvement
Hand deep space concern
Perineal involvement
Immunocompromised host
High risk host features
Neutropenia
Uncontrolled diabetes
Chronic kidney disease
Cirrhosis
Asplenia
Transplant
High risk exam findings
Compartment syndrome features
Neurovascular compromise
Septic arthritis concern
Osteomyelitis concern
Medications
Current and recent medications
Medication reconciliation
Current prescriptions
Recent antibiotics
Recent steroid exposure
Recent chemotherapy
High risk medications
Anticoagulants
Antiplatelets
Immunosuppressants
SGLT2 inhibitors
Allergy profile
Beta lactam allergy
Sulfonamide allergy
Tetracycline allergy
Clindamycin intolerance
Diet
Intake and hydration
Hydration and intake pattern
Poor oral intake
Vomiting limiting intake
Dehydration features
Exposures relevant to infection risk
Alcohol use pattern
Injection drug use context
Nutritional deficiency risk
Review of Systems
System review focused on infection complications
Constitutional
Fever
Chills
Night sweats
Weight loss
Skin
New lesions elsewhere
Diffuse rash
Pruritus
Cardiopulmonary
Chest pain
Dyspnea
Palpitations
Musculoskeletal
Joint pain
Reduced range of motion
Back pain
Neurologic
Weakness
Numbness
Confusion
Collateral History and Family History
Context and transmissible risk
Collateral reliability
Caregiver present
Baseline mental status known
Household and close contact risk
Recurrent boils in household
Close contact MRSA history
Shared towels or sports equipment
Family history relevant comorbidity
Diabetes mellitus (E11.9)
Atopic dermatitis history
Risk Factors
Host and exposure risks
Comorbid risks
Diabetes mellitus (E11.9)
Peripheral vascular disease (I73.9)
Chronic kidney disease (N18.9)
Cirrhosis (K74.60)
HIV infection (B20)
Skin barrier disruption
Eczema
Tinea pedis
Chronic wounds
Lymphedema
Community and healthcare risks
Prior MRSA infection
Recent hospitalization
Recent surgery
Long term care residence
Exposure risks
Injection drug use
Contact sports
Shared razors
Hot tub exposure
Marine water exposure
Special populations
Pregnancy
Pediatric age
Elderly frailty
Immunocompromised
Differential Diagnosis
Tiered differential
Life threatening
Necrotizing fasciitis (M72.6)
Pain out of proportion
Rapid progression hours
Crepitus
Bullae
Fournier gangrene (N49.3)
Perineal pain
Crepitus
Systemic toxicity
Sepsis (A41.9)
Hypotension
Lactate elevated
Altered mental status
Septic arthritis (M00.9)
Pain with passive range of motion
Joint effusion
Fever
Common
Cutaneous abscess (L02.91)
Fluctuance
Purulent drainage
Cellulitis (L03.90)
Diffuse erythema
Warmth
Tenderness
Folliculitis (L73.9)
Small pustules around follicles
Minimal surrounding cellulitis
Hidradenitis suppurativa (L73.2)
Recurrent nodules
Axilla or groin
Sinus tracts
Less common and mimics
Infected epidermoid cyst (L72.0)
Central punctum
Chronic lesion
Herpes zoster (B02.9)
Dermatomal pain
Vesicular rash
Deep vein thrombosis (I82.409)
Unilateral swelling
Risk factors for thrombosis
Allergic contact dermatitis (L23.9)
Itch predominant
Exposure pattern
Gout flare (M10.9)
Joint centered inflammation
Prior gout history
Past Medical History
Prior disease and baseline
Relevant chronic conditions
Diabetes mellitus (E11.9)
Chronic venous insufficiency (I87.2)
Lymphedema (I89.0)
Prior procedures and devices
Prior incision and drainage
Prosthetic joint
Vascular graft
Baseline functional status
Baseline mobility
Baseline ADL independence
Physical Exam
General and vitals
Global assessment
Toxic appearance
Normal appearance
Hydration status
Vital signs pattern
Fever
Tachycardia
Hypotension
Tachypnea
Hypoxia
Skin and soft tissue exam
Lesion characterization
Erythema extent
Warmth
Tenderness
Induration
Fluctuance
Purulence
Necrosis
Bullae
Spread and complications
Lymphangitic streaking
Regional lymphadenopathy
Crepitus
Anatomic region specific
Periorbital exam
Oral and dental source
Hand tendon function
Perineal skin exam
Neurovascular and musculoskeletal
Distal status
Pulses
Capillary refill
Sensation
Motor function
Joint involvement screen
Pain with passive range of motion
Effusion
Range of motion limitation
Lab Studies
Targeted labs by severity
Mild localized abscess without systemic features
No routine labs needed
Pregnancy test when relevant
Moderate to severe infection
CBC
Leukocytosis pattern
Neutropenia risk
BMP
Creatinine for dosing
Sodium for severity context
CRP
Trend support
Nonspecific elevation
Lactate
Sepsis risk stratification
Poor perfusion marker
Microbiology
Purulence culture
Recurrent abscess
Severe infection
Immunocompromised host
Blood cultures
Sepsis physiology
Immunocompromised host
Pitfalls and limitations
Normal labs do not exclude severe soft tissue infection
Early necrotizing infection possible
Immunosuppressed blunted response
Imaging
Scoring Systems
LRINEC score use constraints
Not a rule out tool
Consider only as supportive context
Sepsis screening tools local protocol dependent
qSOFA
NEWS2
MRI
Deep infection assessment
Osteomyelitis concern
Pyomyositis concern
Epidural or deep space concern
Constraints
Time sensitive instability limits use
Contraindications
CT
Indications
Necrotizing infection concern
Deep gas concern
Perineal infection concern
Protocol considerations
IV contrast for deep space delineation
Renal function for contrast risk
Interpretation pearls
Gas in soft tissues
Fascial thickening
Fluid tracking
Ultrasound
POCUS abscess evaluation
Fluid collection
Cobblestoning for cellulitis
Foreign body screening
Pitfalls
Early abscess may be phlegmon
Overlying air limits visualization
Special Tests
Bedside diagnostics and procedures
Aspiration and drainage planning
POCUS guided needle aspiration
Incision and drainage suitability
Septic arthritis pathway when joint concern
Arthrocentesis
Synovial fluid analysis
Gram stain
Culture
ECG
When relevant in skin infection presentations
Indications
Sepsis with tachyarrhythmia concern
Chest pain or dyspnea
High risk patterns
New atrial fibrillation with RVR
Ischemic changes in shock physiology
Assessment
Problem representation and severity
Working diagnosis
Cutaneous abscess (L02.91)
Cellulitis (L03.90)
Severity stratification
Uncomplicated localized infection
Systemic inflammatory response
Deep infection concern
Complications to exclude
Necrotizing soft tissue infection (M72.6)
Septic arthritis (M00.9)
Osteomyelitis (M86.9)
Key support
Fluctuance supports abscess
Diffuse erythema supports cellulitis
Pain out of proportion supports necrotizing concern
Plan
First 5 minutes for the critical patient
Critical workflow
Cardiorespiratory monitoring
Two large bore IV lines when unstable
Oxygen if SpO2 less than 92 percent
Point of care glucose
Lactate if sepsis concern
Early antibiotics for sepsis physiology
Source control
Incision and drainage decision
Fluctuant abscess
Failure of conservative care
Large abscess size
Significant pain
Procedure essentials
Adequate anesthesia
Incision over maximal fluctuance
Break loculations
Irrigation
Avoid routine packing for small uncomplicated abscess
Procedural cautions
Face and periorbital location
Hand deep spaces
Perineal location
Proximity to major vessels
Antibiotics
When antibiotics not required
Small uncomplicated abscess after adequate drainage
No systemic features
When antibiotics favored
Extensive cellulitis surrounding abscess
Systemic features
Immunocompromised host
Extremes of age
Difficult to drain location
Recurrent abscess
Inadequate drainage concern
Empiric MRSA coverage options
TMP SMX DS 1 tablet PO twice daily
Duration 5 to 7 days
Avoid in late pregnancy local protocol dependent
Doxycycline 100 mg PO twice daily
Duration 5 to 7 days
Avoid in pregnancy
Clindamycin 300 to 450 mg PO four times daily
Duration 5 to 7 days
C difficile risk
Streptococcal coverage considerations
Cephalexin 500 mg PO four times daily
Add MRSA agent when purulence risk high
Severe infection IV options
Vancomycin IV local protocol dependent
Weight based dosing local protocol dependent
Renal adjustment required
Cefazolin IV for nonpurulent cellulitis local protocol dependent
Piperacillin tazobactam IV when polymicrobial risk local protocol dependent
Special pathogen risk
Animal bite coverage
Amoxicillin clavulanate 875 mg PO twice daily
Hand bite higher risk
Marine water exposure coverage local protocol dependent
Vibrio risk
Aeromonas risk
Analgesia and supportive care
Pain control
Acetaminophen 1000 mg PO once
Ibuprofen 400 mg PO once
Adjuncts
Elevation
Warm compresses
Reassessment loop
Interval reassessment
Repeat vitals within 30 to 60 minutes if systemic features
Pain and swelling trajectory
Drainage adequacy after procedure
Disposition
Level of care decisions
ICU criteria
Vasopressor requirement
Persistent hypotension after fluids
Rising lactate
Respiratory failure
Inpatient admission criteria
Necrotizing infection concern
Rapid progression
Failed outpatient therapy
Need for IV antibiotics
Inability to perform wound care
Severe immunocompromise
Observation pathway criteria
Moderate cellulitis needing short IV course
Reassessment of response within 12 to 24 hours
Discharge criteria
No systemic toxicity
Pain controlled
Reliable follow up
Wound care feasible
Return precautions understood
Discharge Instructions
Copy discharge instructions
Diagnosis summary
Skin infection with abscess or cellulitis
Area treated today with drainage or antibiotics
Wound care
Keep area clean and dry for 24 hours
Warm compresses 10 to 15 minutes several times daily
Dressing change daily or when soiled
Medications
Take antibiotics exactly as prescribed if given
Pain control with acetaminophen or ibuprofen if safe for you
Activity
Elevate the affected area when possible
Avoid friction or squeezing the lesion
Follow up
Recheck in 24 to 48 hours if worsening
Routine follow up in 2 to 3 days if not improving
Return to ED now if
Fever
Rapidly spreading redness
Severe worsening pain
Confusion
Dizziness or fainting
New numbness or weakness
Black or blistering skin
Trouble moving a nearby joint
References
Guidelines and key sources
Core guidance
Infectious Diseases Society of America skin and soft tissue infections guideline 2014
CDC MRSA clinical overview and prevention resources latest version local protocol dependent
UpToDate skin abscess and cellulitis approach topic review updated periodically local protocol dependent
Supporting evidence
Randomized trials of adjunct antibiotics after abscess drainage showing modest improved cure and reduced recurrence
Emergency medicine procedural references for incision and drainage technique
Source file
Project instructions source
Evidence based clinical reference generator instructions
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.