Gangrene

Question 1

Define gangrene

Answer 1

A complication of necrosis characterised by the decay of body tissues. Results from ischaemia, infection, or trauma (or a combination of these processes).

Question 2

Explain the aetiology/risk factors of necrotising fasciitis

Answer 2

Tissue ischaemia and infarction

Infection

Physical trauma

Thermal injury - burns, fire, radiation etc

Gas gangrene is caused by Clostridia perfringens

Question 3

What are the Two main categories of gangrene?

Answer 3

1. Infectious gangrene (which includes necrotising fasciitis and gas gangrene)
2. Ischaemic gangrene (which can arise from arterial or venous obstruction).

Question 4

What are the risk factors?

Answer 4

Diabetes

Peripheral vascular disease

Leg ulcers - contaminated wounds

Malignancy

Immunosuppression

Steroid use

Puncture/surgical wounds

Prolonged tourniquet use

hypercoagulable states

Question 5

Summarise the epidemiology of gangrene

Answer 5

Gangrene - relatively COMMON

Question 6

Presenting symptoms of gangrene?

Answer 6

1. Risk factors present
2. Pain ;
   Possible hx chronic claudication-type pain in ischaemic gangrene.
   A sudden onset of pain is usually the first symptom of infectious gangrene
3. Oedema and overlying erythema
4. Discolouration of affected area
   - Ecchymoses, purpura, skin blebs, and haemorrhagic bullae may develop in gangrene.
5. Crepitus - crackling noises when fingers run over skin - gas gangrene.

Often affects extremities or areas subject to high pressure

Question 7

Presenting signs of gangrene?

Answer 7

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)

Ischaemic gangrene;
- diminished pedal pulses and ankle BPI

Infectious gangrene;
- Low grade fever and chills

Question 8

Identify appropriate investigations for gangrene and necrotising fasciitis

Answer 8

First lines;
Bloods - 
FBC - anaemic, leukocytosis 
CRP - elevated
Blood culture  - positive culture in infectious gangrene
U&E - low Na, metabolic acidosis

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

Others;
Wound Swab, Pus/Fluid Aspirate - MC&S