General Veterinary Pathology

INFARCTION

• An infarct is an area of coagulative necrosis results due to sudden blockage of an end artery which has no collateral circulation.

Causes

Thrombus / embolus

• Pressure on the vessel wall causing ischaemia
  • Ligatures
  • Decubitus ulcers
  • Torniquets
  • Tumours
  • Cysts / abscess
  • Volvulus / intussusception of intestine
• Contraction of vessel wall

Ergot poisoning

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Smooth muscle contraction

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Narrowing of blood vessel

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Ischaemia

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Seen in extremities (legs, ears, tail, wattles)

• Hypotension ® Shock ® Ischaemia ® Brain infarction

Pathogenesis

Thrombus (blocking of end artery)

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Ischaemia ® capillaries dilate to increase blood supply

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Hypoxia            Area red color [Red infarct]

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Damage to endothelium

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Haemorrhage

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>2 hours - Fusion of RBCs into homogenous mass

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Degeneration of cells

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24hours - Coagulation necrosis of cells

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72hours - Lysis of RBCs

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Release of haemoglobin

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Loss red color [Pale infarct]

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Inflammation

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Scar (yellow / brown due to haemosiderin

Macroscopical appearances

• Red or pale in color
• Cone shaped – apex of cone is at the point of obstruction of vessel - base towards periphery

Infarcts of kidneys

• Common in cows and pigs
• Yellow or pale
• Wedge shaped – seen in cortex
• Apex at arcuate arteries
• Base at capsular end of cortex
• No capsular necrosis
• Appears as healed, depressed areas
• Causes
  • Cardiac vegetations – Corynebacterium pyogenes, streptococci
  • Cows – very common – emboli of uterine vein after parturition

Infarcts of spleen

• Pale or red color
• Seen in borders
• But in dogs, it is band like
• Due to cardiac thrombi

Infarction of intestines

• Common in horses – anterior mesenteric artery (Strongyle worms)
• Whole surface of bowel is affected
• Red in color
• Causes

Volvulus, intussuception, strangulation

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     CVC

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   Necrosis

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 Gangrene

• Sequelae
  • Fatal
  • Toxaemia
  • Shock
  • Peritonitis

Infartion of brain

• Common in man
• Due to arteriosclerosis
• Animals – Dogs – automobile accidents
• Cerebral infarction
• Softening → Myelin engulfed by microglia – “ Compound granular corpuscles”
• Organization or cyst formation (neuroglial cells)
• Cyst with yellow fluid “Apoplectic cysts”

Infarcts of heart

• Common in man due to arteriosclerosis
• Not seen in animals
• Red or pale
• Healed infarcts – Scar
• Sequelae of cardiac infarcts – Myomalacia cardis

Infarcts of liver

• Causes
  • Tumours
  • Thrombus due to Clostridium hemolyticum in bovines
  • Red in colour

Infarcts of lungs

• Common
• Cone shaped
• Red color
• Causes
  • Emboli from
  • Cows – Uterine veins & posterior vena cava (Abscess)
  • Horses – Mesenteric veins
  • Pigs – Pulmonary veins (Hog cholera)
  • Hypostatic congestion
  • Chronic venous congestion
  • Cattle and sheep – Pasteurella infection → Pulmonary infarction (Haemorrhagic septicaemia)

Sequelae of infarcts

• Organization and scar formation
• Gangrene
• Death (Brain, heart, intestine) – SHOCK/ Toxaemia/ Septicaemia