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Definition

Necrotising fasciitis is a potentially life-threatening infection of the fascia (the connective tissue between overlying the muscle). Popularly known as the “flesh-eating disease”.

Fournier’s gangrene – necrotising fasciitis of the perineum

Ludwig’s angina – necrotising fasciitis of the submandibular space


Epidemiology

  • Rare within the UK
  • 70% mortality rate
  • Incidence in the UK is approximately 500 new cases each year
  • Male to female ratio of 3:1

Risk factors

  • Patients who have had a recent wound or bite
  • Patients with diabetes
  • Patients who are immunocompromised
  • Patients with a history of alcohol excess
  • Intravenous drug users
  • Patients with chronic renal or liver disease

Aetiology & Classification

Organisms spread from the subcutaneous tissue along the superficial and deep planes.

Muscle is usually spared but myonecrosis can occur due to compartment syndrome.

Type 1 – polymicrobial infection (aerobic and anaerobic bacteria)

  • Usually seen in the immunocompromised patient

 

Type 2 – Group A Streptococcus: can occur in any age group and in healthy people

 

Type 3 – Gram-negative infection

  • Examples of this are marine organisms (e.g. Vibrio spp. and Aeromonas hydrophilia following seawater contamination)
  • Marine infection can be fatal within 48 hours

 

Type 4 – fungal infection (e.g. candida in the immunocompromised or zygomycetes after traumatic wounds)


Signs & Symptoms

Have a high index of suspicion for necrotising fasciitis as a potential diagnosis if any of the following are present:

  • Rapidly progressive cellulitis
  • Pain out of proportion with clinical findings
  • Systemically, the patient is much more unwell than you would expect from a simple cellulitis

 

On examination

  • The skin will be indurated (red, warm and swollen)
  • There may be crepitus (air in the soft tissues)
  • Discharge from the area has a typical “dishwater” fluid appearance
  • Patients are often critically ill (high-grade temperature, low blood pressure and other signs of septic shock may also be present)

 

Early signs

  • Localised pain, swelling and erythema
  • Poor response to antibiotics
  • Ill-defined margins
  • Systemic illness: malaise, tachycardia, fever

 

Late signs

  • Tense oedema
  • Bullae
  • Skin discolouration
  • Crepitus

 

Very late signs

  • Septic shock
  • Multi-organ failure 
necrotising fasciitis

Example of necrotising fasciitis 5


Diagnosis

Necrotising fasciitis is a clinical diagnosis – if it is clinically felt to be likely, it should be ruled out by surgical exploration.


Investigations

Blood tests:

  • FBC/U&E/CRP/CK/Clotting
  • Group & save
  • Lactate

 

Microbiology:

  • Blood cultures
  • Wound swabs (if applicable)
  • Gram stain and culture of debrided tissue (in theatre)

 

Radiology (should not delay essential surgical management):

  • X-ray or CT can show gas in the soft tissue

 

Bedside finger test:

  • A small incision is made down to the fascia under local anaesthetic and the tissue is probed with a finger
  • In necrotising fasciitis, the tissue will have lost its integrity and will give way too easily to blunt dissection
  • “Dishwater” pus may be present
  • The absence of bleeding is a common finding

Management

This is one of the few plastic surgery emergencies and the plastic surgery registrar should be informed as soon as possible.

Patients usually require immediate transfer to theatre for aggressive surgical debridement.

1. Resuscitate the patient (if haemodynamically unstable or in septic shock)

2. Commence IV antibiotics (this should usually be discussed with the local consultant microbiologist)

  • Antibiotics need to be broad spectrum to cover streptococci, staphylococci, gram-negative rods and anaerobes
  • The choice of antibiotics will depend on where the infection is, the patient’s allergies and swab results when available

3. Consider whether the patient will need to be transferred to an intensive care unit whilst awaiting plastic surgery input


REVIEWED BY

Mr Zakir Shariff

Consultant Plastic Surgeon


References

1. Tidy C. Necrotising Fasciitis. patient.co.uk. 2015 Jul 29. 2495 (v23)

2. Hasham S, Matteucci P, Stanley PR, et al; Necrotising fasciitis. BMJ, 2005 Apr 9 330 (7495):830-3.

3. Brooks A, Cotton BA, Tai N, Mahoney PF. Emergency Surgery Book. Wiley-Blackwell; 1st ed. 2010 Apr 13.

4. Semer NB. Practical Plastic Surgery for Nonsurgeons. Hanley & Belfus, Inc. Philadelphia. 2001

5. By Piotr Smuszkiewicz, Iwona Trojanowska and Hanna Tomczak [CC BY 2.0, via Wikimedia Commons]


 

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