Gangrene

Question 1

What is gangrene?

Answer 1

Tissue necrosis, either wet, dry or gas gangrene

Due to poor vascular supply

Question 2

What is necrotising fasciitis?

Answer 2

Life-threatening infection of deep fascia causing necrosis of subcutaneous tissue.

Question 3

What is the difference between dry and wet gangrene?

Answer 3

Dry: necrosis in absence of infection (ischaemic gangrene)

Wet gangrene: tissue death + infection (infectious gangrene)

Question 4

What is gas gangrene?

Answer 4

subset of necrotising myositis caused by spore-forming Clostridial species

Question 5

What may cause gangrene?

Answer 5

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

Question 6

Describe the aetiology of necrotising fasciitis

Answer 6

Usually polymicrobial involving streptococci, staphylococci, bacterioides + coliforms

Question 7

List 8 risk factors for gangrene and necrotising fasciitis

Answer 7

Diabetes  
Peripheral vascular disease  
Renal disease  
Leg ulcers  
Malignancy  
Immunosuppression  
Drug/alcohol abuse
Steroid use

Question 8

Describe the epidiemiology of gangrene and necrotising fasciitis

Answer 8

Gangrene: relatively COMMON

Necrotising fasciitis + gas gangrene: RARE

Question 9

List 3 features of gangrene

Answer 9

Pain
Black discolouration of affected area
Often affects extremities/ areas subject to high pressure

Question 10

List 3 features of necrotising fasciitis

Answer 10

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

Question 11

Give 2 signs of gangrene

Answer 11

Painful area = erythematous region around gangrenous tissue
Gangrenous tissue = BLACK due to Hb breakdown products

Question 12

How does gas gangrene present?

Answer 12

Rapid onset of myonecrosis, muscle swelling, gas production, sepsis, severe pain
Spreading infection + destruction of tissues causes overlying oedema, discolouration + crepitus (due to gas formation by the infection)

Question 13

Give a sign of dry gangrene

Answer 13

Diminished pedal pulses + ankle-brachial index

Question 14

Give 3 signs of wet gangrene

Answer 14

Tissue becomes boggy with associated pus
Strong odour caused by activity of anaerobes
Low-grade fever + chills

Question 15

List 3 signs of necrotising fasciitis

Answer 15

Area of erythema + oedema
Haemorrhagic blisters may be present
Signs of SIRS + sepsis (high/low temperature, tachypnoea, hypotension)

Question 16

What bloods are taken in gangrene?

Answer 16

FBC (leukocytosis + anaemia)
Met panel (may have met acidosis, liver derangement + renal fail)
U+Es
LDH: elevated with haemolytic anaemia (common in gas gangrene)
Glucose
CRP: elevated
Blood culture

Question 17

What other investigations may be performed in gangrene?

Answer 17

Wound Swab, Pus/Fluid Aspirate: MC+S
X-ray: gas produced in gas gangrene or indicate underlying osteomyelitis
CT/MRI: abscess formation, oedema or thickening of fascia
Doppler US: presence + severity of arterial/ venous obstruction

Question 18

Give 2 additional risk factors for developing ischaemic gangrene

Answer 18

Atherosclerosis

Smoking

Question 19

Give 2 additional risk factors for developing infectious gangrene

Answer 19

Puncture/ surgical wounds

Trauma