Gangrene

Question 1

Define gangrene

Answer 1

Death of tissue from poor vascular supply (sign of critical ischaemia)

Complication of necrosis characterised by decay of body tissues

2 main categories: ischaemic (dry) and infectious gangrene (wet)

Question 2

Aetiology of gangrene

Answer 2

Ischaemic: Atherosclerosis | diabetes-associated microangiopathy | thrombosis | IVDU | vasculitis | malignancy | antiphospholipid syndrome

Infectious: group A beta-haemolytic strep species | staph | non-group A strep | enterobacteriaceae

Gas: spore-forming gram +ve anaerobic clostridial species - C. perfringens

Question 3

Risk factors for gangrene

Answer 3

Diabetes mellitus 
Trauma 
Malignancy 
Atherosclerosis 
Smoking 
Renal disease
Drug and alcohol abuse
Contaminate wounds
Immunosuppression 
Malnutrition

Question 4

Symptoms of gangrene

Answer 4

Rapid onset severe pain + muscle swelling/oedema + gas production + skin discolouration

Question 5

Signs of gangrene

Answer 5

Crepitus (gas)
Sepsis 
Myonecrosis
Diminished pedal pulses and ABI (ischaemic)
Low grade fever + chills (infectious)
Cold extremities

Question 6

Investigations for gangrene

Answer 6

Rapid progression, spread or clinical deterioration -> surgical exploration / biopsy to identify if the fascia is involved (necrotising fasciitis)

Bloods:
FBC (leucocytosis, haemochromatosis, anaemia)
CRP+ESR (elevated)
LDH (elevated in haemolytic anaemia)
Metabolic panel (metabolic acidosis , liver or renal derangement)
Blood cultures (infectious)

Plain X-rays (gas in soft tissues or osteomyelitis)

CT/MRI (abscess formation or evidence of enhancement, oedema or fascia involvement)

Doppler (indicate presence + severity of arterial or venous obstruction