General Veterinary Pathology

TYPES OF OEDEMA

1. Inflammatory oedema
2. Cardiac oedema
3. Renal oedema
4. Hunger/Famine/War oedema
5. Pulmonary oedema
6. Cachetic oedema
7. Myxoedema
8. Parasitic oedema
9. Angioneurotic oedema
10. Brisket disease

1. Inflammtory oedma

• Toxins damage blood vessels - Increased permeability of endothelium - Fluid rich in protein pass out - “INFLAMMATORY EXUDATE”

2. Cardiac oedema

• Congestive heart failure leads to CVC which results  in insufficient renal circulation ischaemia leading to oliguria with diminished chloride excetion. This results in sodium retention which raises tissue osmotic pressure aggrevating oedema

Oedema - Abdominal cavity - Ascites

• Causes for cardiac oedema
• Increased hydrostatic pressure of blood
• Increased vascular permeability
• Sodium retention
• Symptoms
• Oedema of dependant parts
• Traumatic pericarditis in bovines

Cardiac oedema may develop in  horses with chronic vesicular emphysema.

3. Renal oedema

• In acute glomerulonephritis (in man), oedema in face and eyelids are usually seen.
  • Causes of acute glomerulonephritis are
    • Decreased osmotic pressure of blood
      • Toxins damage glomerular capillaries resulting in albuminuria and hypoproteinaemia.
    • Increased osmotic pressure of ECF
      • In acute nephritis, oliguria / Anuria results in sodium retention
    • Increased capillary permeability
    • Increased hydrostatic pressure in capillaries in venous side
      • Toxins damage kidney and heart causing cardiac failure and its outcome is CVC
• Subacue nephritis and nephrosis
  • Decreased colloidal osmotic pressure of blood
  • Increased sodium retention
  • Hypoalbuminaemia stimulates adrenal cortex to secrete increased amount of aldosterone which helps in reabsorption of sodium chloride. This retained salt increases osmotic pressure and cause oedema.
• Chronic glomerulonephrtis
  • Hypertension for long period throws great strain on heart resulting in heart failure and thereby causing CVC which increases blood pressure in capillaries. As a resut of this, oedema occurs.

4. Hunger / Famine / war oedema 

• Hypoproteinaemia → Decreased plasma osmotic pressure
• War / famine → Decreased protein availability

5. Pulmonary oedema

• Causes
• Cardiac failure - hypertension; valvular disease - pericarditis
• Renal lesions
• Pressure on pulmonary veins by neoplasm
• Injury to brain
• Rapid removal of effusion from pleural / peritoneal cavity
• Poisons
• Infections

Oedema - Lung - Rib markings

6. Cachetic oedema

• Anaemia
• Wasting diseases
• Malnutrition
• Cardiac illness

7. Myxoedma

• This occurs in chronic thyroid deficiency. In this condition there will be increased protein accumulation in tissue fluid which raises pressure of fluid locally and water is drawn into the site.

8. Parasitic oedema

• This type of oedema is most commonly seen in animals suffering with stomach worms, liver flukes, amphistomes. During migratory life of cercaria, haemorrhage & necrosis occurs in liver. Adult flukes inhabitats bileduct causing chronic irritation of lining mucosa of the duct resulting in cirrhosis. Affected liver cannot synthesis protein leading to oedema formation.
• Due to hypoproteinemia, there will be an accumulation of fluid in lower jaw called  as “BOTTLE JAW” which is a characteristic feature of parasitic oedema.

9. Angioneurotic oedema

• In man, allergens like snake venom produces hypersensitivity reaction which increases capillary permeability resulting in oedema in lips, glottis, thorax
• In animals (cattle, horses), endogenous / exogenous allergens (plant, protein; fish meal) cause release of histamine which damage blood vessels and oedema results.

10. Brisket disease

• Cattle moved to high altitude 9000ft above sea level develop oedema in abdomen, brisket, neck and jowl.
• At high altitudes, partial pressure of oxygen is decreased. The resulting hypoxia develops polycythemia (Increased viscosity of blood) and polypnoea (Increased heart beat). Cardiac muscle becomes degenerated as it works in hypoxic condition and hence hypertrophied heart slowly dilates and which draws valves downwards resulting in valvuar incompetency and gives rise to chronic venous congestion.
• Reason for development of oedema in high altitude
  • Hypoxia
  • Chronic venous congestion - Develops due to increased capillary blood pressure and hypoxia