Gangrene Pathology

14 Questions

What causes putrefaction in gangrene?

Saprophytic bacteria that break down protein

What is gangrene defined as?

Massive tissue necrosis followed by putrefaction

What is the difference between dry and moist gangrene?

Dry gangrene occurs in tissues with poor blood supply and moist gangrene occurs in tissues with good body fluid

What happens when gangrene reaches an area with good blood supply?

Gangrene stops advancing

What is the purpose of the line of demarcation?

To separate healthy from gangrenous tissue

What is the result of the invasion of saprophytic bacteria in necrotic tissue?

Putrefaction and foul odour of tissue

What is the result of the drainage and evaporation of fluids in dry gangrene?

Tissue becomes dry and shrunken

What is the significance of the groove that forms in the conical stump?

It separates healthy from necrotic tissue

What is the characteristic of moist gangrene?

Rapid spread of toxins and rapid putrefaction

What is the definition of infective gangrene?

A type of gangrene caused by bacterial infection

When is it likely to see moist gangrene in a limb?

After a crushed limb injury

What is gas gangrene mainly of?

Muscles

What is the effect of Saccharolytic bacteria in gas gangrene?

Produce powerful toxins and enzymes that cause tissue necrosis and hemolysis of RBCs

What is the clinical picture of a patient in shock?

The patient is confused, skin is pale and cold, and pulse is rapid

Study Notes

Circulatory Disturbances: Gangrene

Definition: Massive tissue necrosis followed by putrefaction
Causes: Necrosis caused by sudden ischemia or bacterial toxins, putrefaction caused by saprophytic bacteria breaking down protein of necrotic tissue

Types of Gangrene

Dry gangrene
Moist gangrene
Infective gangrene
Gas gangrene

Dry Gangrene

Occurs in limbs with arterial occlusion (e.g. thrombus, embolus, surgical ligature)
Pathological features:
- Massive necrosis occurs distal to site of occlusion
- Dryness of necrotic tissue due to drainage and evaporation of fluids
- Saprophytic bacteria invade necrotic tissue causing putrefaction and bad odour
- Tissue attains black stain due to hydrogen sulfide units with iron of hemoglobin
- Gangrenous process advances slowly along the limb as inflammation causes thrombosis within the vessels
- Toxins of putrefaction irritate adjacent tissue, causing zone of acute inflammation in neighboring healthy part (line of demarcation)
- Granulation tissue grows towards gangrenous part with formation of groove (line of separation)

Line of Demarcation and Separation

Line of demarcation: Narrow zone of inflammation between healthy and gangrenous tissue
Line of separation: Groove between healthy and necrotic zone, level of tissue separation
Line of demarcation is above line of separation

Moist Gangrene

Causes: Sudden arterial and venous occlusion
Occurs mainly in internal organs where no evaporation of fluids can occur
Rapid spread of toxins and rapid putrefaction due to presence of fluids
Line of demarcation is poor, line of separation is absent, and toxemia is marked
Seen in crushed limb injuries and diabetic patients due to hyperglycemia and poor body resistance

Infective Gangrene

Definition: Subtype of moist gangrene where bacteria cause both necrosis and putrefaction
Example: Cancrum oris caused by treponema Vicenti and bacillus fusiformis

Gas Gangrene

Definition: Moist gangrene mainly of muscles, occurring in deep wounds contaminated by manured soil containing anaerobic spores
Caused by saccharolytic bacteria (e.g. Cl. Welchi) or proteolytic bacteria (e.g. Cl. sporogens)
Tissue destruction causes ischemia that facilitates germination of spores
Gangrenous tissue stains red or black depending on the type of bacteria

Shock

Definition: State of tissue hypoperfusion due to inadequate effective circulating blood volume
Clinical picture:
- Confused patient
- Pale and cold skin
- Rapid weak pulse, low blood pressure, and shallow rapid breathing