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Define edema?

Edema is defined as the excessive or uncontrolled collection of fluid within interstitial space and/air body cavities.

The net movement of fluid between plasma & interstitium governed by hydrostatic pressure & plasma oncotic pressure.

edema

Hemodynamic Disorders

In edema, approximately 60% of lean body weight is water, 2/3rd of which is intracellular and the remainder is in extracellular compartments, mostly as interstitial fluid; only 5% of total body water is in blood plasma.

Edema in different body cavities are variously designated;

  • In pleural cavity: Hydrothorax (pleural effusion)
  • In pericardium: Hydropericardium (pericardial effusion)
  • In peritoneum: Hydroperitoneum (ascites)
  • Anasarca is serious & generalized edemas with profound subcutaneous tissue swelling.

Types

  • Transudate
    • Protein poor in fluid and low LDH
    • Specific Gravity- 1.012
    • It is Clear and It is caused by;
      • Increased hydrostatic pressure and decreased osmotic pressure
      • It is seen in patients suffering from heart failure, renal failure, hepatic failure, and certain forms of malnutrition.
  • Exudate
    • Protein-rich in this fluid and high LDH
    • Specific gravity-1.020
    • It is cloudy due to the presence of white cells
    • It is caused by increased vascular permeability (Inflammation).

Causes 

  • Increased hydrostatic pressure
  • Reduced plasma osmotic pressure (hypoproteinemia)
  • Lymphatic obstruction
  • Sodium and water retention
  • Inflammation
  1. Increased hydrostatic pressure
    • Impaired venous return
    • Congestive heart failure
    • Constrictive pericarditis
    • Liver cirrhosis
    • Venous obstruction or compression
    • Thrombosis
    • External pressure (e.g. mass)
    • Lower extremity inactivity with prolonged dependency
    • Arteriolar dilation Heat
    • Neurohumoral dysregulation
  2. Reduced plasma osmotic pressure (Hypoproteinemia)
    • It occurs when albumin, the major plasma protein, is not synthesized in adequate amounts as in severe liver diseases (e.g., cirrhosis or protein malnutrition)
    • It is lost from the circulation as in nephrotic syndrome
    • It lessened plasma osmotic pressure when fluid goes to interstitial tissues.
      • Protein-losing glomerulopathies (nephrotic syndrome)
      • Liver cirrhosis (ascites)
      • Malnutrition
      • Protein-losing gastroenteropathy
  3. Lymphatic obstruction
    • Inflammatory
    • Parasitic infestation
    • Elephantiasis:
      • Lymphatic obstruction due to substantial inguinal lymphatic & lymph node fibrosis then edema of the external genitalia & lower limbs and finally elephantiasis occurs.
    • Neoplastic condition
    • Postsurgical ( e.g. modified radical mastectomy for carcinoma of breast)
    • Post-irradiation
  4. Sodium and water retention
    • Excessive salt intake with renal insufficiency
    • Increased tubular reabsorption of sodium
    • Renal hypoperfusion
    • Increased renin-angiotensin-aldosterone secretion
  5. Inflammation
    • Acute inflammation
    • Chronic inflammation
    • Angiogenesis

Morphology of edema

  • Gross:
    • Distribution is influenced by gravity
    • As independent edema (e.g.’ the legs when standing, the sacrum when recumbent)
    • Pitting edema
    • Lungs (pulmonary edema)
    • The cut, section shows heavy boggy lungs, & frothy blood-tinged fluid.
    • Brain- swollen with narrowed sulci and  distended gyri 
    • Periorbital edema-severe renal disease
  • Microscopically:
    • Clearing & separation of extracellular matrix & swelling of subtle.
 

Clinical features

  • Subcutaneous edema
    • It is a signal of underlying cardiac disease or renal disease; impairment wound healing, clearance of infections
  • Pulmonary edema
    • Left ventricular failure; Renal failure
      • Impaired oxygen diffusion
      • Favors bacterial infection
  • Body cavities effusion
    • Pleural effusion- a collapse of lung parenchyma
    • Ascites- a bacterial infection
    • Pericardial effusion- heart failure
  • Cerebral edema
    • Herniation of brain material through the foramen magnum- injure medullary centers & death.

 

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