Edema Formation

Edema is excessive fluid accumulation in interstitial spaces.

Location

Edema can develop in any organ or collect as free fluid in body cavities (such as ascites, pleural effusion, pericardial effusion)

Factors promoting the development of edema

Edema may occur because of:

1. Excessive fluid filtration out of capillaries, which can be due to :
   • Elevated hydrostatic pressure usually due to heart failure (see Starlings Forces) or over-hydration
   • Reduced plasma colloid osmotic pressure (hypoproteinemia) which itself can be due to:
     • Excessive protein loss from the kidneys or GI tract
     • Reduced production from the liver
   • Increased capillary membrane permeability
2. Lymphatic obstruction