Gangrene

Question 1

What is gangrene?

Answer 1

tissue necrosis 
- either wet with superimposed infection, dry or gas gangrene – due to poor vascular supply

Question 2

What are the different types of gangrene a patient may have?

Answer 2

1. Dry gangrene: necrosis in absence of infection
2. Wet gangrene: tissue death and infection
3. Gas gangrene: subset of necrotising myositis caused by spore-forming Clostridial species

Question 3

What is necrotising fasciitis?

Answer 3

a life-threatening infection of deep fascia causing necrosis of subcutaneous tissue.

Question 4

What are some causes of gangrene?

Answer 4

o Tissue ischaemia and infarction (critical limb ischaemia)
o Physical trauma
o Thermal injury
o Gas gangrene is caused by Clostridia perfringens

Question 5

What causes necrotising fasciitis?

Answer 5

o Usually polymicrobial involving streptococci, staphylococci, bacterioides and coliforms

Question 6

What are the risk factors of gangrene?

Answer 6

o Diabetes
o Peripheral vascular disease
o Leg ulcers
o Malignancy
o Immunosuppression
o Steroid use
o Puncture/surgical wounds
o Trauma

Question 7

Summarise the epidemiology of gangrene and necrotising fasciitis

Answer 7

● Gangrene - relatively COMMON
● Necrotising fasciitis and gas gangrene - RARE

Question 8

What are the presenting symptoms of gangrene?

Answer 8

o Pain
o Discolouration of affected area - black
o Often affects extremities or areas subject to high pressure
o feeling of heaviness in affected area
o oedema + swelling
1. Wet (Infectious) Gangrene ⇒ low-grade fever & chills
- Poorly demarcated necrotic area
2. Dry (Ischaemic) Gangrene ⇒ diminished pulses & ABPI (no signs of infection)
- Well demarcated necrotic area
3. Gas Gangrene ⇒ darkened skin. Crepitus may be heard due to escaping gas. Infective area gives off distinct and potent smell. May be able to visualise gas on radiograph (air bubbles on x-ray), rapid onset of myonecrosis, muscle swelling, sepsis, severe pain

Question 9

What are the presenting symptoms of necrotising fasciitis?

Answer 9

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

Question 10

What signs of gangrene can be found on physical examination?

Answer 10

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

Question 11

What signs of necrotising fasciitis can be found on physical examination?

Answer 11

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

Question 12

What investigations are used to diganose/ monitor gangrene?

Answer 12

1. Blood Cultures → if infectious gangrene suspected
2. Doppler Ultrasonography → may indicate presence and severity of arterial or venous obstruction
3. Surgical Exploration & Skin Biopsy → only definitive method to make the diagnosis

Question 13

How is gangrene managed?

Answer 13

1. Wet Gangrene (nec fasc and gas gangrene) → surgical debridement and broad-spectrum antibiotics
2. Dry Gangrene → IV heparin and surgical revascularisation
   - Consider amputation if limb is non-viable