Gangrene

Question 1

What is gangrene?

Answer 1

Complication of necrosis characterised by decay of body tissues
Infectious (wet) or ischaemic (dry)

Question 2

What is the most common cause of gangrene?

Answer 2

Critically insufficient blood supply
Often a/w diabetes + long-term smoking

Question 3

What are the subtypes of infectious gangrene?

Answer 3

Necrotising bacterial infection
Necrotising fasciitis
Gas gangrene

Question 4

How is necrotising fasciitis classified?

Answer 4

Type 1: caused by mixed anaerobes + aerobes (often occurs post-surgery in diabetics). Most common type
Type 2: caused by Streptococcus pyogenes

Question 5

List 4 risk factors for necrotising fasciitis

Answer 5

Skin factors: trauma, burns, soft tissue infection
DM (most common pre-existing medical condition) esp. if treated with SGLT2 inhibitors
IV drug use
Immunosuppression

Question 6

What is the most commonly affected site in necrotising fasciitis?

Answer 6

Perineum (Fournier’s gangrene)

Question 7

List 4 S/S of wet gangrene

Answer 7

Pain
Swelling + erythema
Discharge/ frank pus
Foul smelling odour

Question 8

List 4 S/S of dry gangrene

Answer 8

Coldness + pallor in affected region.
Numbness.
+/- Erythema
No discharge.

Question 9

Describe symptoms of necrotising fasciitis

Answer 9

Acute onset pain, swelling, erythema
Extremely tender over infected tissue with hypoaesthesia to light touch
Fever + tachycardia may be absent or occur late

Question 10

How does necrotising fasciitis often present?

Answer 10

Rapidly worsening cellulitis with pain out of keeping with physical features

Question 11

What bloods are taken in suspected gangrene?

Answer 11

FBC
U+Es
CRP
LDH
Blood cultures
Glucose
Coagulation panel

Question 12

What imaging may be performed in gangrene?

Answer 12

XR
CT

Question 13

Describe management of necrotising fasciitis

Answer 13

Urgent surgical referral + debridement
Vancomycin + Tazocin IV

Question 14

Describe management of gas gangrene

Answer 14

Surgical debridement +/- amputation
Benzylpenicillin + Clindamycin IV

Question 15

Describe management of ischaemic gangrene

Answer 15

IV Heparin bolus followed by continuous heparin infusion
Threatened viability: surgical revascularisation +/- amputation
Viable extremity: Thrombolytic therapy

Question 16

What is necrotising fasciitis?

Answer 16

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

Question 17

What is the difference between dry and wet gangrene?

Answer 17

Dry: necrosis in absence of infection (ischaemic gangrene)
Wet gangrene: tissue death + infection (infectious gangrene)

Question 18

What is gas gangrene?

Answer 18

subset of necrotising myositis caused by spore-forming Clostridial species esp. Clostridium perfringens

Question 19

List 8 risk factors for gangrene and necrotising fasciitis

Answer 19

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

Question 20

Describe the epidiemiology of gangrene and necrotising fasciitis

Answer 20

Gangrene: relatively COMMON
Necrotising fasciitis + gas gangrene: RARE

Question 21

Why does gangrene appear black?

Answer 21

Due to Hb breakdown products

Question 22

How does gas gangrene present?

Answer 22

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 23

Give a sign of dry gangrene

Answer 23

Diminished pedal pulses + ankle-brachial index

Question 24

What other investigations may be performed in gangrene?

Answer 24

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 25

Give 2 risk factors for developing ischaemic gangrene

Answer 25

Atherosclerosis
Smoking

Question 26

Give 2 risk factors for developing infectious gangrene

Answer 26

Puncture/ surgical wounds
Trauma