What is edema? Edema is a noticeable increase in the volume of interstitial fluid. Depending on the cause of the edema, it may be observed unilaterally, bilaterally, locally, or as a generalized presentation.

Pathogenesis of edema

Fluid exchange within the intra- and extravascular spaces is done using the vascular and lymphatic system, and is managed by regulating the starling forces. Changes within these systems or the equilibrium of the fluid exchange can influence the development of edema.

Which conditions cause edema?

Any clinical conditions or medications that alter the function of the vascular system, lymphatic system, or starling forces may cause edema. Some conditions may cause changes to more than one of the influencing factors. 

  1. Increased capillary hydrostatic pressure
    • Congestive heart failure
    • Primary renal failure
    • Retention of sodium
  1. Decreased oncotic pressure.
    • Malnutrition
    • Nephrotic syndrome
  1. Damage of or increased permeability in the capillary endothelium
    • Localized inflammation
    • Allergic reaction
  1. Dysfunction of the lymphatic system.
    • Surgical removal
    • Lymphedema
    • Filariasis

Source: Fauci, A., Brauwald, E., Kasper, D., Hauser, S., Longo, D., Jameson, L. J., & Loscalzo, J. (2008). Harrison’s Principles of Internal Medicine (17th ed.). McGraw Hill / Medical.