Cellulitis, Emergency Medicine

Basics

Description

Acute, spreading erythematous superficial infection of skin and SC tissues:
- Variety of pathogens
- Extension into deeper tissues can result in necrotizing soft tissue infection
Progressive spread of erythema, warmth, pain, and tenderness
Predisposing factors:
- Lymphedema
- Tinea pedis
- Open wounds
- Pre-existing skin lesion (furuncle)
- Prior trauma or surgery
- Retained foreign body
- Vascular or immune compromise
- Injection drug use

Etiology

Simple cellulitis:
- Group A streptococci
- Staphylococcus aureus-including resistant strains such as community-associated methicillin-resistant S. aureus (CA-MRSA; see below):
  - CA-MRSA risk factors include: Prior MRSA infection, household contact of CA-MRSA patient, daycare contact of MRSA patients, children, soldiers, incarcerated persons, athletes in contact sports, IV drug users, men who have sex with men
  - Different antibiotic susceptibility than nosocomial MRSA
  - CA-MRSA now sufficiently prevalent to warrant empiric treatment
  - Suspect CA-MRSA in unresponsive infections
Nosocomial MRSA:
- Risk factors: Recent hospital or long-term care admission, surgery, injection drug use, vascular catheter, dialysis, recent antibiotic use, unresponsive infection
- Resistant to most antibiotics (see "Treatment")
Extremity cellulitis after lymphatic disruption:
- Nongroup A β-hemolytic streptococci (groups C, B, G)
Cellulitis in diabetics:
- Can be polymicrobial with S. aureus, streptococci, gram-negative bacteria, and anaerobes, especially when associated with skin ulcers
Periorbital cellulitis:
- S. aureus
- Streptococcal species
Buccal cellulitis:
- Haemophilus influenzae type B
- Anaerobic oral flora, associated with intraoral laceration or dental abscess
Less common causes:
- Clostridia
- Anthrax
- Pasteurella multocida-common after cat and dog bites
- Eikenella corrodens-human bites
- Pseudomonas aeruginosa:
  - Hot-tub folliculitis-self-limited
  - Foot puncture wound
  - Ecthyma gangrenosum in neutropenic patients
- Erysipelothrix species-raw fish, poultry, meat, or hide handlers
- Aeromonas hydrophila-freshwater swimming
- Vibrio species-seawater or raw seafood

Facial cellulitis in children:
- Streptococcus pneumoniae
- H. influenzae type B, although incidence declining since introduction of HIB vaccine
Perianal cellulitis:
- Group A streptococci
- Associated or antecedent pharyngitis or impetigo
Neonates:
- Group B streptococci

Diagnosis

Signs and Symptoms

Common to all syndromes:
- Pain, tenderness, warmth
- Erythema
- Edema or induration
- Fever/chills
- Tender regional lymphadenopathy
- Lymphangitis
- Accompanying SC abscess possible
- Suspect deep abscess especially if treatment failure on initial antibiotic
- Superficial vesicles
Buccal cellulitis:
- Odontogenic cases more serious:
  - Toothache, sore throat, or facial swelling
  - Progressive extension into soft tissues of neck with fever, erythema, neck swelling, and dysphagia

Facial cellulitis in children:
- Erythema and swelling of the cheek and eyelid
- Rapidly progressive
- Usually unilateral
- Upper respiratory tract symptoms
- Risk for cavernous sinus thrombosis and permanent optic nerve injury
Perianal cellulitis:
- Erythema and pruritus extending from the anus several centimeters onto adjacent skin
- Pain on defecation
- Blood-streaked stools

History
Patients often incorrectly attribute CA-MRSA infection with spontaneous abscess to a spider bite
Physical Exam
In simple cellulitis, physical findings can suggest the etiology and help narrow empiric antibiotic coverage:

Staph etiology: Focal abscess or pustule with: Fluctuance, yellow or white center, central point or "head," or draining pus, indolent progression
Strep etiology: Sharply demarcated borders, lymphangitis, pre-existing lymphedema, concomitant nausea from toxin

Essential Workup

Cellulitis is a clinical diagnosis.
Physical exam to reveal infection source

Diagnosis Tests & Interpretation

Lab

WBC generally unnecessary
Gram stain and culture to focus antimicrobial selection and reveal resistant pathogens (MRSA):
- Aspirate point of maximal inflammation or punch biopsy if there is no wound to culture
- Perform in treatment failures and consider in admitted patients
Blood culture:
- Usually negative in uncomplicated cellulitis
- May identify organism in patients with:
  - Lymphedema
  - Buccal or periorbital cellulitis
  - Saltwater or freshwater source
  - Fever or chills

Imaging

Plain radiographs may reveal abscess formation, SC gas, or foreign bodies:
- Extension to bone (osteomyelitis) not visualized early on plain radiographs
Extremity vascular imaging (Doppler US) can help rule out deep venous thrombosis (DVT).
US useful for diagnosing abscess if physical exam is equivocal or if there is a broad area of cellulitis
- In cellulitis may see characteristic "cobblestone" appearance and thickening of SC layer, both due to edema
CT or MRI can help rule out necrotizing fasciitis

Differential Diagnosis

Necrotizing fasciitis
Lymphangitis or lymphadenitis
Thrombophlebitis or DVT:
- Differentiation from cellulitis:
  - Absence of initial traumatic or infectious focus
  - No regional lymphadenopathy
  - Presence of risk factors for DVT
Insect bite
Allergic reaction
Acute gout or pseudogout
Ruptured Baker cyst
Herpetic whitlow
Neoplasm
Phytophotodermatitis
Erythema chronicum migrans lesion of Lyme disease
Differential diagnosis of facial cellulitis:
- Allergic angioedema
- Conjunctivitis
- Contusion

Differential diagnosis of perianal cellulitis:

Candida intertrigo
Psoriasis
Pinworm infection
Child abuse
Behavioral problem
Inflammatory bowel disease

Treatment

Initial Stabilization/Therapy

Airway compromise possible with deep extension of facial or neck cellulitis

Ed Treatment/Procedures

General principles:
- Consider local prevalence of resistant pathogens in addition to usual causes
- In simple cellulitis, periorbital cellulitis, and diabetic patients, need to include CA-MRSA coverage in empiric therapy
- Usual outpatient treatment: 7-10 days
- Cool compresses for comfort
- Analgesics
- Extremity elevation
- Treat predisposing tinea pedis with topical antifungal such as clotrimazole
Simple cellulitis:
- Outpatient:
  - Oral Cephalexin + TMP/SMX (to cover CA-MRSA)
  - Alternatives to cephalexin: Oral dicloxacillin, macrolide, or levofloxacin
  - Alternatives to TMP/SMX: Clindamycin or Doxycycline
- Inpatient:
  - IV nafcillin or equivalent, + IV vancomycin (to cover CA-MRSA)
Extremity cellulitis after lymphatic disruption:
- Same as simple cellulitis
Cellulitis in diabetics:
- Outpatient:
  - Amoxicillin/clavulanate + TMP/SMX (to cover CA-MRSA), or clindamycin
- Inpatient:
  - IV ampicillin/sulbactam or imipenem cilastatin or equivalent; + IV vancomycin (to cover CA-MRSA)
Periorbital cellulitis in adults:
- Outpatient: Oral dicloxacillin or azithromycin; + TMP/SMX (to cover CA-MRSA)
- Inpatient: IV vancomycin
Buccal cellulitis in adults:
- Outpatient: Oral amoxicillin/clavulanate
- Inpatient: IV ceftriaxone
- Odontogenic source:
  - Drainage essential
  - Coverage for anaerobes: Clindamycin
Facial cellulitis in children:
- IV ceftriaxone
Perianal cellulitis:
- Outpatient: Oral penicillin VK
- Inpatient: IV penicillin G (aqueous)
Animal or human bite:
- Oral amoxicillin/clavulanate
Foot puncture wound:
- Oral or IV ciprofloxacin or IV ceftazidime
MRSA:
- Nosocomial MRSA: IV vancomycin or oral or IV linezolid
- CA-MRSA:
  - PO: TMP/SMX, clindamycin or doxycycline
  - IV: Vancomycin or clindamycin

Medication

Amoxicillin/clavulanate: 500-875 mg (peds: 45 mg/kg/24h) PO BID or 250-500 mg (peds: 40 mg/kg/24h) PO TID
Ampicillin/sulbactam: 1.5-3 g (peds: 100-300 mg/kg/24h up to 40 kg; over 40 kg give adult dose) IV q6h
Azithromycin: (Adults and peds) 10 mg/kg up to 500 mg PO on day 1, followed by 5 mg/kg up to 250 mg PO daily on days 2-5
Ceftazidime: 500-1,000 mg (peds: 150 mg/kg/24h; max. 6 g/24h; use sodium formulation in peds) IV q8h
Ceftriaxone: 1-2 g (peds: 50-75 mg/kg/24h) IV daily
Cephalexin: 500 mg (peds: 50-100 mg/kg/24h) PO QID
Ciprofloxacin: (Adult only) 500-750 mg PO BID or 400 mg IV q8-12h
Clindamycin: 450-900 mg (peds: 20-40 mg/kg/24h) PO or IV q6h
Dicloxacillin: 125-500 mg (peds: 12.5-25 mg/kg/24h) PO q6h
Doxycycline: 100 mg PO BID for adults
Erythromycin base: (Adult) 250-500 mg PO QID
Imipenem cilastatin: 500-1,000 mg (peds: 15-25 mg/kg) IV q6h; max. 4 g/24h or 50 mg/kg/24h, whichever is less
Levofloxacin: (Adult only) 500-750 mg PO or IV daily
Linezolid: 600 mg PO or IV q12h (peds: 30 mg/kg/24h div. q8h)
Nafcillin: 1-2 g IV q4h (peds: 50-100 mg/kg/24h divided q6h); max. 12 g/24h
Penicillin VK: 250-500 mg (peds: 25-50 mg/kg/24h) PO q6h
Penicillin G (aqueous): 4 mU (peds: 100,000-400,000 U/kg/24h) IV q4h
Trimethoprim/sulfamethoxazole (TMP/SMX): 2 DS tabs PO q12h (peds: 6-10 mg/kg/24h TMP div. q12h)
Vancomycin: 1 g IV q12h (peds: 10 mg/kg IV q6h; dosing adjustments required younger than age 5 yr); check serum levels

Follow-Up

Disposition

Admission Criteria

Toxic appearing
Tissue necrosis
History of immune suppression
Concurrent chronic medical illnesses
Unable to take oral medications
Unreliable patients

Discharge Criteria

Mild infection in a nontoxic-appearing patient
Able to take oral antibiotics
No history of immune suppression or concurrent medical problems
No hand or face involvement
Has adequate follow-up within 24-48 hr

Follow-Up Recommendations

Follow-up within 24-48 hr
Sooner if worsening symptoms, including new or worsening lymphangitis, increasing area of redness, worsening fever
Outline the border of erythema before discharge to aid in assessing response to therapy

Pearls and Pitfalls

Strep and staph are most common causes
CA-MRSA now significant cause of cellulitis, frequent enough to warrant including coverage in empiric treatment
Clinicians not accurate at identifying MRSA at the bedside
A deep abscess may be misclassified as cellulitis
Use clinical suspicion and ultrasound to avoid missing an abscess

Additional Reading

Abrahamian FM, Talan DA, Moran GJ. Management of skin and soft-tissue infections in the emergency department. Infect Dis Clin North Am. 2008;22:89-116.
Gunderson CG. Cellulitis: Definition, etiology, and clinical features. Am J Med. 2011;124:1113-1122.
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;52:1-38.
Pasternack MS, Swartz MN. Cellulitis, necrotizing fasciitis and subcutaneous tissue infections. In: Mandell GL, Bennett JE, Dolin R, eds. Mandell, Douglas and Bennetts Principles and Practice of Infectious Diseases. 7th ed. New York, NY: Elsevier/Churchill Livingstone; 2010:1289-1312.
Phoenix G, Das S, Joshi M. Diagnosis and management of cellulitis. BMJ. 2012;345:e4955.
Swartz MN. Cellulitis. New Engl J Med. 2004;350:904-912.

Codes

ICD9

682.3 Cellulitis and abscess of upper arm and forearm
682.6 Cellulitis and abscess of leg, except foot
682.9 Cellulitis and abscess of unspecified sites
682.0 Cellulitis and abscess of face
682.1 Cellulitis and abscess of neck
682.2 Cellulitis and abscess of trunk
682.4 Cellulitis and abscess of hand, except fingers and thumb
682.5 Cellulitis and abscess of buttock
682.7 Cellulitis and abscess of foot, except toes
682.8 Cellulitis and abscess of other specified sites
682 Other cellulitis and abscess

ICD10

H05.019 Cellulitis of unspecified orbit
L03.90 Cellulitis, unspecified
L03.119 Cellulitis of unspecified part of limb
L03.211 Cellulitis of face
L03.011 Cellulitis of right finger
L03.012 Cellulitis of left finger
L03.019 Cellulitis of unspecified finger
L03.01 Cellulitis of finger
L03.031 Cellulitis of right toe
L03.032 Cellulitis of left toe
L03.039 Cellulitis of unspecified toe
L03.03 Cellulitis of toe
L03.111 Cellulitis of right axilla
L03.112 Cellulitis of left axilla
L03.113 Cellulitis of right upper limb
L03.114 Cellulitis of left upper limb
L03.115 Cellulitis of right lower limb
L03.116 Cellulitis of left lower limb
L03.11 Cellulitis of other parts of limb
L03.1 Cellulitis and acute lymphangitis of other parts of limb
L03.221 Cellulitis of neck
L03.311 Cellulitis of abdominal wall
L03.312 Cellulitis of back [any part except buttock]
L03.313 Cellulitis of chest wall
L03.314 Cellulitis of groin
L03.315 Cellulitis of perineum
L03.316 Cellulitis of umbilicus
L03.317 Cellulitis of buttock
L03.319 Cellulitis of trunk, unspecified
L03.31 Cellulitis of trunk
L03.811 Cellulitis of head [any part, except face]
L03.818 Cellulitis of other sites
L03.81 Cellulitis of other sites

SNOMED

128045006 cellulitis (disorder)
449671007 Cellulitis of upper limb (disorder)
449710006 Cellulitis of lower limb (disorder)
194005002 orbital cellulitis (disorder)
123951002 cellulitis of skin (disorder)
200652002 cellulitis of face (disorder)
239162003 Wound cellulitis (disorder)
30584002 Cellulitis of back, except buttock (disorder)
46876003 Cellulitis of trunk (disorder)

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