Gangrene

Question 1

Define gangrene and summarise its aetiology and epidemiology

Answer 1

Definition: tissue necrosis, either wet with superimposed infection, dry (ischemiac) or gas gangrene

Aetiology:

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

Risk factors:

• Diabetes
• Peripheral vascular disease
• Leg ulcers
• Malignancy
• Immuosuppression
• Steroid use
• Puncture/surgical wounds

Gangrene is relatively common

Question 2

Describe the history/presenting symptoms of gangrene

Answer 2

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

Question 3

What are the signs of gangrene upon physical examination?

Answer 3

• Painful region tends to be erythematous region around gangrenous tissue
• Gangrenous tissue is black because of haemoglobin break down product
• 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
• Oedema
• Diminished pedal pulses and ankle-brachial index (ischaemic gangrene)
• Low-grade fever and chills (infectious gangrene)

Question 4

What investigations are used to identify gangrene?

Answer 4

1st investigations to order:
- FBC, U&Es, glucose, CRP and blood culture (expected result leukocytosis, haemoconcentration, or anaemia )
- Comprehensive metabolic panel (may indicate metabolic acidosis, liver derangement, renal failure )
- Serum LDH (elevated if haemolytic anaemia.)
• Rapidly developing haemolytic anaemia with an increased lactate dehydrogenase level is common in patients with gas gangrene.
- Coagulation panel- perform as baseline
- Wound swab, pus/fluid aspirate- MC&S

Investigations to consider:

• Surgical exploration and skin biopsy
• CT angiography
• Magnetic resonance angiography (MRA)
• CT chest and abdomen
• X-ray of affected area- may show gas produced in gas gangrene