Following are the various causes of edema except:
Approximately 60% of lean body weight is water, two-thirds of which is intracellular. Most of the  remaining water is found in extracellular compartments in the form of interstitial fluid; only 5% of the body’s water is in blood plasma.  As noted earlier, edema is an accumulation of interstitial fluid within tissues. 

Increases in hydrostatic pressure are mainly caused by disorders that impair venous return. Local increases in intravascular pressure caused, for example, by deep venous thrombosis in the lower extremity can cause edema restricted to the distal portion of the affected leg.
Reduction of plasma albumin concentrations leads to decreased colloid osmotic pressure of the blood and loss of fluid from the circulation.
Edema may result from lymphatic obstruction that compromises resorption of fluid from interstitial spaces.

Robbins BASIC  PATHOLOGY T E N T H   E D I T I O N page no.99
Increase in hydrostatic pressure
Decreased colloid osmotic pressure
Due to lymphatic obstruction
Decrease in intravascular pressure