Oedema

Accumulation of fluid in the interstitial spaces

Pathophysiology

Causes of oedema

Raised capillary pressure
  • Arteriolar dilation
  • Raised venous pressure
    • LV failure → pulmonary oedema
    • RV failure → peripheral oedema
Reduced plasma osmotic pressure
  • Can be caused by malnutrition, protein malabsorption, excessive renal excretion of protein, hepatic failure
Lymphatic insufficiency
  • Lymph node damage
  • Filariasis (parasitic disease which can cause elephantiasis)
Changes in capillary permeability
  • Inflammation
  • Histamine

Types of oedema

  • Pulmonary oedema: accumulation of fluid in the interstitial and intra-alveolar lung spaces
    • Diffusion distance decreases so gas exchange compromised
  • Peripheral oedema: oedema in tissues perfused by the peripheral vascular system, usually in the lower limbs
  • See ‘Heart Failure’ notes for more detail