What is Necrotizing Fasciitis?
Necrotizing fasciitis is a life-threatening, rapidly spreading soft tissue infection characterized by necrosis of the fascia, subcutaneous tissue, and potentially deeper structures, requiring immediate surgical debridement to prevent death. 1
Definition and Pathophysiology
Necrotizing fasciitis is a severe invasive infection involving any or all layers of the soft-tissue compartment, from superficial dermis to deep fascia and muscle. 1 The infection spreads along fascial planes with secondary necrosis of overlying tissues, distinguishing it from simple cellulitis. 1, 2
Microbiology
The infection can be classified by bacterial etiology:
Monomicrobial infections (Type 2):
- Group A Streptococcus (S. pyogenes) - most common, with mortality approaching 50-70% when associated with hypotension and organ failure 1
- Staphylococcus aureus (including MRSA) 1
- Vibrio vulnificus, Aeromonas hydrophila 1
- Anaerobic streptococci (Peptostreptococcus species) 1
Polymicrobial infections (Type 1):
- Average of 5 pathogens per wound, with up to 15 different organisms possible 1
- Predominantly bowel or genitourinary flora (coliforms and anaerobes) 1
- Associated with post-surgical infections, decubitus ulcers, perianal abscesses, injection drug use, or Bartholin gland infections 1
Clinical Presentation
Cardinal Diagnostic Features
The diagnosis is frequently missed initially (85-100% of cases), as it often resembles cellulitis. 2 Key distinguishing features include:
- Severe pain disproportionate to physical findings - the most important early clinical indicator 1, 3
- "Wooden-hard" feel of subcutaneous tissue extending beyond visible skin involvement 1
- Systemic toxicity with altered mental status 1
- Failure to respond to initial antibiotic therapy 1
- Edema or tenderness extending beyond cutaneous erythema 1
- Crepitus (gas in tissues) 1
- Bullous lesions 1
- Skin necrosis or ecchymoses 1
Laboratory Findings
- Dramatically elevated CRP levels (5-fold higher than cellulitis) 3
- Elevated serum urea and creatinine predict higher mortality 4
- Low hemoglobin levels associated with worse outcomes 4
- Poor white blood cell response, particularly in diabetic patients, correlates with higher mortality 4
Diagnosis
Clinical judgment remains the most important diagnostic element. 1 A high index of suspicion is paramount, as clinical scoring systems are more useful for excluding rather than confirming necrotizing infections. 1
Imaging
CT or MRI may show edema extending along fascial planes, but imaging should never delay surgical consultation and definitive treatment. 1 The sensitivity and specificity of these modalities remain poorly defined. 1
Definitive Diagnosis
The gold standard is direct surgical visualization showing: 1
- Swollen, dull gray fascia with stringy necrosis
- Thin, brownish exudate (not true pus)
- Extensive undermining of tissues
- Easy dissection of tissue planes with blunt instrument or gloved finger
When necrotizing fasciitis is suspected but not confirmed, exploratory incision in the area of maximum suspicion provides both diagnosis and treatment with minimal morbidity. 1
Treatment
Surgical Management (Primary Intervention)
Immediate aggressive surgical debridement is the cornerstone of treatment and must not be delayed. 1
- Return to operating room every 24-36 hours for repeat debridement until no further necrosis is evident 1
- Early amputation may be necessary in 27.8% of cases, with diabetes mellitus significantly increasing amputation risk 5, 4
- Mean number of surgical interventions is approximately seven 5
Antimicrobial Therapy
For polymicrobial necrotizing fasciitis, empiric coverage must include agents effective against aerobes (including MRSA) and anaerobes: 1
Vancomycin, linezolid, or daptomycin PLUS one of:
- Piperacillin-tazobactam
- Carbapenem (imipenem-cilastatin, meropenem, or ertapenem)
- Ceftriaxone plus metronidazole
- Fluoroquinolone plus metronidazole
For Group A streptococcal infections: 1
- Clindamycin PLUS penicillin
- Clindamycin suppresses toxin and cytokine production and is superior to penicillin alone in animal models 1
Duration: Continue antibiotics until no further debridement is needed, clinical improvement occurs, and fever has been absent for 48-72 hours. 1
Supportive Care
- Aggressive fluid resuscitation is mandatory, as wounds discharge copious tissue fluid 1
- Intensive care management for sepsis and organ failure 1
- Mean hospitalization is 32 days, including 8 days in ICU 5