Gangrene

Question 1

Gangrene, a severe condition typified by localised tissue necrosis (death). There are two primary types of gangrene, dry and wet. Which of these is due to chronic ischaemia, and is characterised by mummification of the affected tissue without bacterial invasion?

Answer 1

• dry

Wet is characterised by necrotic tissue infected with bacteria, leading to liquefaction and is more commonly associated with acute arterial occlusion or venous congestion.

Question 2

There is also gas gangrene, which is a subsection of wet gangrene that causes crepitus and gas production. What infection is this commonly caused by?

1 - staphylococcus aureas
2 - streptococcus pyrogens
3 - clostridium perfringen
4 - klebsiella

Answer 2

3 - clostridium perfringen

Typically occurs following surgery or trauma with soil or faecal matter involved

Fourniers gangrene is another variant of wet gangrene and involves the genitals and perineum

Question 3

All of the following conditions cause dry gangrene due to chronic ischaemia, EXCEPT which one?

1 - Peripheral Arterial Disease (PAD)
2 - Surgical complications
3 - Diabetes Mellitus
4 - Vasculitis (Buerger’s disease and SLE)

Answer 3

2 - Surgical complications

Question 4

All of the following are risk factors for wet gangrene due to tissue injury and bacterial infection that develops rapidly due to blockage in venous or arterial blood flow coupled with bacterial invasion, EXCEPT which one?

1 - Critical Limb Ischaemia
2 - Surgical Wounds or Trauma
3 - Immunosuppression
4 - Severe Burns or Frostbite
5 - Multiple sclerosis

Answer 4

5 - Multiple sclerosis

Question 5

Which of the following laboratory tests is least useful when attempting to diagnose and identify the cause of gas gangrene?

1 - Blood cultures
2 - Tissue cultures
3 - TFTs and amylase
4 - FBC, U&E, LFTs
5 - CRP and ESR

Answer 5

3 - TFTs and amylase

• Blood and tissue culture help identify organism and provide tailored treatment.

Question 5

Gangrene can cause which of the following clinical presentations?

1 - fever
2 - paraesthesia
3 - hypotension
4 - multi-system involvement
5 - changes in skin appearance
6 - tissue loss
7 - all of the above

Answer 5

7 - all of the above

Changes can be local and systemic

Question 5

Gangrene involves a typically standard disease progression. Which of the following is NOT one nof these stages?

1 - ischaemia and hypoxia
2 - anaerobic metabolism
3 - rehealing and proliferation
4 - Tissue Necrosis
5 - Bacterial Infection
6 - Toxin Production
7 - Progression

Answer 5

3 - rehealing and proliferation

• Ischaemia and hypoxia = tissue ischaemia and hypoxia
• Anaerobic metabolism - cells switch for a short term t compensate for hypoxia
• Tissue Necrosis = irreversible cell and tissue damage leading to tissue death
• Bacterial Infection = once established, bacteria rapidly proliferate at site of necrosis and spread
• Toxin Production = Clostridium perfringens produce alpha-toxin which causes haemolysis and tissue destruction.
• Progression = may progress to sepsis, multi-organ failure and even death.

Question 6

What is the major difference between gangrene and necrotising fasciitis (NEC)?

1 - NEC is caused by tissue death
2 - NEC is caused by reduced blood flow
3 - NEC can progress to sepsis
4 - NEC is caused by bacterial infection

Answer 6

4 - NEC is caused by bacterial infection

Question 7

Which of the following imaging modalities is used when trying to identify the cause of gangrene?

1 - X-rays
2 - Computed Tomography (CT) scan
3 - Magnetic Resonance Imaging (MRI)
4 - Duplex Ultrasound
5 - all of the above

Answer 7

5 - all of the above

• X-rays = good for identifying gas bubbles in gas gangrene and show signs of PAD such as calcified vessels.
• CT = good for tissue involvement in wet or gas gangrene, and identifying abscesses or other complications.
• MRI = good for soft tissue infection and determining the extent of tissue necrosis.
• Duplex Ultrasound = good for evaluating vascular status in suspected cases of dry gangrene

Question 8

Once the diagnosis is confirmed, all of the following can be initiated:

• Surgical Management for debridement of necrotic tissue with good margins of surrounding tissue. Amputation may also be needed
• Antibiotic Therapy is guided by blood and tissue samples, BUT waiting for results should not delay broad spectrum antibiotic administration

Hyperbaric Oxygen Therapy may be used in specialised centres to increase oxygen delivery to tissues.

Treatment of Underlying Conditions

Vascular surgery may be needed for patients with peripheral artery disease to restore blood flow.

Optimise other comorbidities such as good glycemic control