What is the cause of Fournier gangrene?

Causes of Fournier Gangrene

Fournier gangrene is primarily caused by polymicrobial infection originating from the perianal, genitourinary, or cutaneous sources, with mixed aerobic and anaerobic bacteria invading fascial planes through compromised tissue barriers in susceptible hosts.

Etiology and Pathogenesis

Fournier gangrene is a necrotizing fasciitis affecting the perineal, genital, or perianal regions. The infection typically has three main sources of origin:

1. Perianal/Colorectal Source (21%) 1

   • Anorectal infections
   • Perianal abscesses
   • Rectal malignancies
   • Colorectal trauma

2. Genitourinary Source (19%) 1

   • Urethral strictures
   • Urinary tract infections
   • Periurethral gland infections
   • Urinary catheterization complications

3. Cutaneous Source (24%) 1

   • Local skin trauma
   • Genital trauma
   • Dermatologic conditions

4. Idiopathic (36%) - Cases where no clear source can be identified 1

Microbiology

The infection is typically polymicrobial with synergistic action between:

• Aerobic bacteria:

  • Staphylococcus aureus (including MRSA)
  • Escherichia coli
  • Pseudomonas species
  • Streptococcus species 1

• Anaerobic bacteria:

  • Bacteroides
  • Clostridium
  • Peptostreptococcus 1

Pathophysiology

The disease progresses through a specific pathophysiological sequence:

1. Initial infection: Bacteria enter through a breach in the mucosal or cutaneous barrier
2. Inflammatory response: Leads to obliterative endarteritis
3. Vascular thrombosis: Causes ischemia of surrounding tissues
4. Tissue necrosis: Reduced blood flow promotes anaerobic bacterial proliferation
5. Fascial spread: Infection spreads rapidly along fascial planes 1

The infection typically spreads along the Colles' fascia, Scarpa's fascia, and Buck's fascia, which explains the rapid progression to the abdominal wall and thighs. The testes are usually spared due to their separate blood supply 1.

Risk Factors

Several conditions increase susceptibility to Fournier gangrene:

• Diabetes mellitus (most common) 1
• Obesity 1
• Immunocompromised states (HIV, leukemia) 1
• Alcoholism 1
• Malnutrition 1
• Recent urethral or perineal surgery 1
• Advanced age 1

Clinical Presentation

The infection can present:

• Insidiously: With gradual onset of symptoms
• Abruptly: With rapid progression to systemic toxicity 1

Initial symptoms include:

• Intense perineal/scrotal pain (often disproportionate to visible findings)
• Erythema and swelling
• Fever and tachycardia
• Later progression to cutaneous necrosis and crepitus 1

Diagnostic Considerations

Early diagnosis is crucial for survival. The Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score and Fournier's Gangrene Severity Index (FGSI) are useful tools for diagnosis and prognosis, respectively 1.

Management Principles

Treatment requires a multifaceted approach:

1. Prompt surgical debridement - The cornerstone of treatment
2. Broad-spectrum antibiotics covering gram-positive, gram-negative, and anaerobic organisms
3. Hemodynamic support and intensive care
4. Nutritional support
5. Wound care and possible reconstructive surgery 1

Complications and Prognosis

Without prompt treatment, Fournier gangrene can rapidly progress to:

• Septic shock
• Multiple organ failure
• Death (mortality rates vary from 7.5% to 88% in different studies) 1

Early diagnosis and aggressive surgical and medical management are essential to improve outcomes in this life-threatening condition.