Different types of necrosis in animals

1. Necrosis
Dr. Jeny K John
Asst. Professor (Veterinary Clinical Pathology)
Sardar Vallabhbhai Patel University of Agriculture and technology,
Meerut

2. Necrosis
 Local death of tissues within the living individual
It is the sequence of morphological changes that follow cell death in living
tissue or organ, resulting from the progressively degradative action of
enzymes on the irreversibly injured cell.
Most common: Coagulative necrosis characterized by denaturation of
cytoplasmic protein, break down of cell organelles, and cell swelling
Morphological appearance of necrosis is due to 1. denaturation of proteins
2. enzymatic digestion of the cell
Digestion by either autolysis (digestive enzymes from lysosomes of dead
cell) or heterolysis (lysosome of infiltrating leukocytes)

3. Etiology
1. Poisons
a. Chemical poisons: strong acids, alkalies, drugs, insecticides, fungicides
and other toxic chemicals like phenol, mercuric chloride etc
b. Toxins of pathogenic organisms: toxins produced by bacteria, viruses,
fungi, rickettsiae, protozoa and metazoan parasites
Salmonella, fusobacterium and staphylococcus: necrosis of tissues
c. Plant poisons: alkaloids cause necrosis
• Plants of Senecia species in large amount: hepatotoxic and produce hepatic
necrosis in cattles
• Mushrooms contain a toxic glycoside phallin: renal tubular necrosis
• Croton oil: necrosis of epithelium in the skin and mucus membrane
d. Animal poisons: Cantharidin from beetles and bee stings cause focal
necrosis of tissues, parasites also cause necrosis

4. Etiology
2. Disturbances in circulation
a. Ischaemia or loss of blood supply
Thrombus, embolism, compression of artery by tumour, abcess, cyst,
ligature, tourniquet, ergot poisoning
b.Passive hyperemia
Torsion, volvulus, strangulation of intestine
c. General anemia
Necrosis of brain

5. Etiology
3. Mechanical injuries:
It will cause necrosis when tissue are crushed or when blood supply is injured
or destroyed
4. Thermal changes: both heat and cold
Frostbite
5. Electric current: produced by lightening or generators may coagulate or
char tissues
6. X-ray and nuclear fission substances: Protoplasmic alteration that result in
necrosis

6. Macroscopic appearance
• Grey, white or yellow in colour
• Appear as if the tissues are coagulated or cooked and stand out
distinctly from the surrounding normal tissue
• Borders are sharply demarcated and are usually surrounded by a red
zone of inflammatory reaction
• If pyogenic bacteria present, abscess may form and when putrefactive
bacteria enter gangrene may occur

7. Microscopic appearance
Increased eosinophilia
 Due to loss of normal basophilia imparted by RNA to the
cytoplasm
 Increased binding of eosin to the denatured intracytoplasmic
proteins
Cell outlines are indistinct or absent
Cells having more glassy homogenous appearance mainly due to loss
of glycogen particles
Cytoplasm appears vacuolated or moth eaten
Calcification of necrotic cells may occur

8. Nuclear changes
1. Basophiilia of the chromatin may fade-KARYOLYSIS due to the
action of DNAses of lysosomal origin
2. PYKNOSIS characterized by nuclear shrinkage and increased
basophilia
3. KARYORRHEXIS pyknotic nucleus undergoes fragmentation

9. Types of necrosis
1. Coagulative necrosis
• Most common type
• Characterized by preservation of the basic structural outline of the
coagulated cells or tissue for at least some days
• Nucleus is usually lost but the basic cellular shape is preserved
 The architectural detail of the area persists but the cellular
details is lost
 Denaturation of structural and enzymatic proteins in the
cytoplasm blocks the proteolysis of the cell, and thus the tissue
architecture is maintained

10. Eg.
• Hypoxic death of organs except brain
• Infarct is a best example.
• F. necrophorum- liver of cattle
• Muscular dystrophy in cattle and sheep associated with Vit E
deficiency
• Renal tubular epithelium in mercury, thalium or uranium poisoning
• Skin, mucous membrane or wound following application of
concentrated phenol

11. Macroscopically
• Necrotic area is firm and rather dry in consistency
• It has homogenous, opaque, cooked appearance and is grey, white or
tan
Microscopically
• Architectural outline of the tissue or organ is maintained but the
cellular details are lost

12. Result
• Area does not attract neutrophils
• Leukocytes appears slowly
• Dead material remain in the area for a long period of time
• Necrotic cells are removed by fragmentation and phagocytosis of the
cellular debris by the action of proteolytic lysosomal enzymes of
leukocytes

13. 2. Liquefactive necrosis
• This type of necrosis is characterized by transformation of the tissue
into a liquid mass in which cellular and architectural detail is lost
• It is due to action of lysosomal enzymes
• Seen in focal bacterial infection
• Chemicals like turpentine
• abscesses., suppurative wound infection
• Hypoxic death of brain, CO, cyanide poisoning, thiamine deficiency in
cat, Vitamin E deficiency in chickens, mouldy maize poisoning in
horses

14. Macroscopically
• The tissue in the area is liquefied and may be watery, tenacious or semisolid in
consistency
• Color is white, yellow or red
• Long standing case: CT formation
Microscopically
• No Architectural or cellular detail is visible in the area of necrosis
• Dead tissue is homogenous and stains pink with eosin
• If bacteria are present, neutrophils in varying degree of disintegration are found
• Entire necrotic mass is surrounded by a zone of acute or chronic inflammation

15. 3. Caseous necrosis
• Characterized by conversion of dead tissue into a homogenous
granular mass resembling cheese and by the absence of both
architectural and cellular details
• Term caseous means cheesy and is derived from the white and cheesy
appearance of the area of necrosis
• Seen in TB, caseous lymphadenitis in sheep, oesophagostomiasis in
sheep

16. Macroscopically
• Area of necrosis is a granular amorphous material resembling cheese.
• Mass is dry but creamy in consistency
• It is soft, friable and white grey in colour
• Calcium salts are frequently deposited in the dead tissue
• Caseous mass is enclosed within a CT capsule
Microscopically
• Necrotic foci is composed of structure less, amorphous granular debris
enclosed within a distinctive ring of granulomatous inflammation
• Neither architectural nor cellular detail is present
• Calcification commonly occurs in the necrotic areas especially in sheep and
cattle

17. 4. Fat necrosis
• Death of the adipose tissue within the living individual
• 3 types: pancreatic, traumatic and nutritional
a. Pancreatic fat necrosis
• Death of adipose tissue in the vicinity of the pancreas due to the action of
lipases
• Caused by some injury to the pancreas or its duct
• Primary or secondary tumors of the pancreas
• Pancreatitis
• Powerful lipases from the pancreas destroy not only the pancreatic
substance itself, but also the adipose tissue in and around the pancreas and
throughout the peritoneal cavity
• Activated pancreatic enzymes liquefy fat cell membranes and hydrolyze the
triglycerides esters contained within them
• Released fatty acids combine with calcium to produce grossly visible chalky
white areas (fat saponification)

18. Macroscopically
• Necrotic fat appears as white or yellowish white, chalky, opaque masses in
the interstitial adipose tissue of the pancreas an in peripancreatic fat
• A zone of acute or chronic inflammation appears around the necrotic areas
• Connective tissue may undergo metaplasia and produce bone, seen in the
abdominal fat of the pig and cattle
Microscopically
Only shadowy outlines of necrotic fat cells may be seen, with basophilic
calcium deposits and a surrounding inflammatory reaction

19. b. Traumatic fat necrosis
• Death of the adipose tissue in an area of mechanical injury
• Commonly occurs in subcutaneous adipose tissue due to mechanical
injuries during working, fighting or excercising
Eg. Canine from dog bites, in backs of fat pigs from injury produced by
erysipelas
Macroscopically, fat appears firm, opaque, chalky mass in the area of
injury surrounded by a zone of acute and chronic inflammatory reaction

20. c. Nutritional fat necrosis
• Necrobiotic alteration in fat that is associated with extreme emaciation
and debility
• Occurs in starving or debilitated animals usually observed in cattle and
sheep in TB and JD
• Necrosis may occur throughout the body but is most common in the
abdominal fat
Macroscopically, fat appears firm, opaque, chalky mass
It may undergoes calcification
Microscopically, the adipose cells contain a pale pink slightly granular
material in which numerous clefts and crystals are seen.
Chronic inflammatory reaction occurs at the junction of the necrotic and
living tissue