Gangrene and necrotising fasciitis

Question 1

Define

Answer 1

DEFINITION:

Gangrene - tissue necrosis, either wet with superimposed infection, dry or gas gangrene

Necrotising Fasciitis - a life-threatening infection that spreads rapidly across fascial planes

Question 2

Causes

Answer 2

Gangrene

• Tissue ischaemia and infarction
• Physical trauma
• Thermal injury
• Gas gangrene is caused by Clostridia perfringens

Necrotising Fasciitis
- Usually polymicrobial involving streptococci, staphylococci, bacterioides and coliforms

Question 3

Risk factors

Answer 3

Diabetes

Peripheral vascular disease

Leg ulcers

Malignancy

Immunosuppression

Steroid use

Puncture/surgical wounds

Question 4

Epidemiology

Answer 4

Gangrene - relatively COMMON

Necrotising fasciitis and gas gangrene - RARE

Question 5

Symptoms

Answer 5

Gangrene:

• Pain
• Discolouration of affected area
• Often affects extremities or areas subject to high pressure

Necrotising Fasciitis
Pain
- Often seems SEVERE and out of proportion to the apparent physical signs
Predisposing event (e.g. trauma, ulcer, surgery)

Question 6

Signs

Answer 6

Gangrene

• Painful area = erythematous region around gangrenous tissue
• Gangrenous tissue = BLACK because of haemoglobin break down products
• Wet Gangrene - tissue becomes boggy with associated pus and a strong odour caused by the activity of anaerobes
• Gas Gangrene - spreading infection and destruction of tissues causes overlying oedema, discolouration and crepitus (due to gas formation by the infection)

Necrotising Fasciitis

• Area of erythema and oedema
• Haemorrhagic blisters may be present
• Signs of systemic inflammatory response and sepsis (high/low temperature, tachypnoea, hypotension)

Question 7

Investigations

Answer 7

Bloods - FBC, U&Es, glucose, CRP and blood culture

Wound Swab, Pus/Fluid Aspirate - MC&S

X-ray of affected area - may show gas produced in gas gangrene