Great feedback everyone...
Here is my take: Edema (swollen tissue) often results from increased capillary blood pressure (as someone stated). Forces favoring filtration are increased while secretion pressures may not change very much. This could results from dilation of the arterioles or from venous congestion extending back to the capillaries, as may occur in heart failure(this was mentioned).
ALSO
Edema can result from problems with lymph drainage. Lymphatics serve as an overflow system, returning excess tissue fluid and proteins to the circulation. When lymph drainage is poor, proteins accumulate in tissue spaces and compromise the secretion pressure gradient. This can happen because of lymph vessel obstruction, such as parasitic invation.
Just thought I would add that to the thought process....