Fournier's Gangrene
Summary
Fournier's Gangrene is a fulminant Necrotising Fasciitis of the perineum and genitalia (scrotum/penis in men, labia in women). It is a urological/surgical emergency characterised by obliterative endarteritis of the subcutaneous arteries, resulting in rapid, extensive tissue necrosis. The infection is typically Polymicrobial and synergistic (aerobes + anaerobes). Without immediate radical debridement, mortality is high (20-40%). [1,2]
Key Facts
- Spare the Testes: The testes are almost always spared because their blood supply (Testicular Artery) comes from the abdomen (aorta) and is separate from the affected scrotal fascia (Pudendal supply).
- Speed: The infection can spread along fascial planes (Dartos -> Colles -> Scarpa's) at a rate of 2-3 cm per hour. "Time is Tissue".
- Diabetes: The single biggest risk factor (present in >60% of cases).
Clinical Pearls
Pain Out of Proportion: This is the classic hallmark. The patient is screaming in pain, but the skin might only look slightly red or even normal initially. This is because the damage is deep in the fascia and nerves.
The "Finger Test": If uncertain, perform a bedside incision under local anaesthetic. If the finger passes easily along the fascial plane without resistance (due to lysis of connections) and yields "dishwater pus", it is Nec Fasc.
Don't wait for the Scanner: If you feel crepitus or see gangrene, go straight to theatre. CT causes fatal delays.
Demographics
- Ratio: Men 10 : 1 Women.
- Age: Peak >50 years.
- Risk Factors:
- Diabetes Mellitus (Poor microvasculature + Immune dysfunction).
- Alcoholism.
- Immunosuppression (HIV, Steroids).
- Portal of Entry: Perianal abscess, urethral structure, catheterisation, recent surgery/biopsy.
Mechanism
- Inoculation: Bacteria enter subcutaneous space via a breach (anus/urethra/skin).
- Synergy: Aerobes (E. coli) consume oxygen, creating a hypoxic environment for Anaerobes (Bacteroides/Clostridium) to thrive.
- Enzymes: Bacteria produce collagenases/hyaluronidases which liquefy the fascia.
- Thrombosis: Endotoxins cause thrombosis of nutrient vessels (endarteritis) -> Skin necrosis (black eschar).
- Gas: Glucose fermentation produces gas (Subcutaneous Emphysema/Crepitus).
Symptoms
Signs
- Genitalia: Examine perineum, scrotum, penis.
- Rectal Exam: Look for perianal abscess or fistula as source.
- Abdomen: Check for spread to abdominal wall (Scarpa's fascia).
Bloods
- High WCC + CRP.
- Hyponatraemia: Common in severe sepsis.
- LRINEC Score (Lab Risk Indicator for Necrotising Fasciitis):
- Uses CRP, WBC, Hb, Na, Creatinine, Glucose.
- Score ≥6 indicates high risk. Warning: Do not rely on this to exclude diagnosis.
Imaging
- CT Pelvis:
- Finding: Subcutaneous gas. Stranding. Source (e.g. rectal abscess).
- Benefit: Shows extent of spread (e.g. into pelvis/thigh).
- Caution: Only if patient is stable. Theatre takes priority.
Management Algorithm
SUSPECTED FOURNIER'S
(Pain, Erythema, Toxicity)
↓
RESUSCITATE (Sepsis 6)
(IV Fluids, Oxygen, Catheter)
↓
START ANTIBIOTICS (Immediate)
(Meropenem + Clindamycin + Vancomycin)
↓
EMERGENCY SURGERY
(Radical Debridement)
↓
┌─────────────┴─────────────┐
ICU SUPPORT LOOK AGAIN
(Inotropes) (Planned return to
(Ventilation) Theatre in 24h)
1. Surgical (Source Control)
- Radical Debridement: Excision of ALL necrotic tissue until healthy, bleeding tissue is reached.
- "If in doubt, cut it out".
- Scrotum is left open (secondary intention).
- Testes are often left hanging exposed (pouched in thighs later).
- Colostomy: May be needed if faecal contamination is the source (Perianal abscess).
2. Antibiotics (Triple Therapy)
- Gram Negative: Meropenem or Piperacillin-Tazobactam.
- Gram Positive (MRSA): Vancomycin or Linezolid.
- Toxin Suppression: Clindamycin. (Inhibits ribosomal protein synthesis, stopping Strep/Staph from making exotoxins).
3. Adjuncts
- Hyperbaric Oxygen: Controversial. May inhibit anaerobes and promote healing, but logistics difficult for unstable patients.
- IVIG: For Group A Strep toxic shock.
- Sepsis: Multi-organ failure (Renal, Respiratory).
- Disfigurement: Loss of scrotal skin/penile skin. Requires skin grafting.
- Ketoacidosis: In diabetics.
- Mortality: 20-40%. Higher if delay to surgery >24 hours or extensive spread.
- Morbidity: Long hospital stay, multiple surgeries, skin grafts.
Key Guidelines
| Guideline | Organisation | Key Recommendations |
|---|---|---|
| Urological Infections | EAU | Broad spectrum abx active against Rectal and Urethral flora. Urgent debridement. |
| Sepsis | Surviving Sepsis | Antibiotics within 1 hour. Early source control. |
Landmark Knowledge
1. Clindamycin Mechanism
- Why add Clindamycin if Meropenem kills the bacteria?
- "Eagle Effect": Beta-lactams (Meropenem) work on cell walls of dividing bacteria. In high inoculum (heavy load), bacteria stop dividing (stationary phase), making penicillin less effective. Clindamycin works on ribosomes (protein synthesis) regardless of division and stops TOXIN production.
What is Fournier's Gangrene?
It is a very severe, fast-spreading infection of the private parts. "Gangrene" means the tissue dies.
How did it start?
Bacteria from the gut or skin got under the surface, usually through a small scratch, boil, or abscess. Because of conditions like diabetes, the immune system couldn't stop it, and it spread wildly.
Is it serious?
Yes, it is critical. Without surgery, it is fatal.
What does the surgery involve?
Surgeons have to cut away all the infected black skin and fat to stop the spread. This often leaves a large open wound which will need special dressings and maybe plastic surgery later to fix.
Primary Sources
- Bonkat G, et al. EAU Guidelines on Urological Infections. European Association of Urology. 2023.
- Mallikarjuna MN, et al. Fournier's Gangrene: current practices. ISRN Urol. 2012.
- Wong, CH et al. The LRINEC (Laboratory Risk Indicator for Necrotizing Fasciitis) score. Crit Care Med. 2004.
Common Exam Questions
- Surgery: "Patient with Diabetes, scrotal pain, crepitus. Diagnosis?"
- Answer: Fournier's Gangrene.
- Anatomy: "Why are testes spared?"
- Answer: Independent blood supply (Testicular artery from Aorta) vs Scrotal skin (Pudendal artery).
- Microbiology: "Role of Clindamycin?"
- Answer: Toxin suppression (Protein synthesis inhibitor).
- Management: "First definitive step?"
- Answer: Surgical Debridement (Not CT, Not Abx - Surgery is prime).
Viva Points
- Meleney's Gangrene: Similar but affects abdominal wall (post-surgery).
- Antibiotic Penetration: Why debride? Dead tissue has no blood supply. Antibiotics cannot reach the bacteria in the gangrene. Only a knife can remove them.
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.