Causes of Edema

• Increased capillary hydrostatic pressure: causes can include the following:

  • –  Marked increase in blood flow, e.g., vasodilation in a given vascular bed

  • –  Increasing venous pressure, e.g., venous obstruction or heart failure

  • –  Elevated blood volume (typically the result of Na+ retention), e.g., heart failure

• Increased interstitial oncotic pressure: primary cause is thyroid dysfunction (elevated mucopolysaccharides in the interstitium)

  •   – These act as osmotic agents resulting in fluid accumulation and a non- pitting edema. Lymphedema (see below) can also increase πIF.

• Decreased vascular oncotic pressure: causes can include the following:

• –  Liver failure
• –  Nephrotic syndrome 

Increased capillary permeability : Circulating agents, e.g., tumor necrosis factor alpha (TNF-alpha), bradykinin, histamine, cytokines related to burn trauma, etc., increase fluid (and possibly protein) filtra- tion resulting in edema.

• Lymphatic obstruction/removal (lymphedema): causes can include the following:

–  Filarial (W. bancrofti—elephantitis)
–  Bacterial lymphangitis (streptococci)
–  Trauma
–  Surgery
–  Tumor 

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