Why does a person develop anasarca (generalized edema)? The patient is a known CVA, known Diabetic (mellitus)?

The patient is a known CVA, known Diabetic (mellitus) and has Aspiration Pneumonia… she developed generalized edema eventhough her kidneys are properly working and is excreting adequate amount of urine… how does glucose play a role in edema?

please help i need to answer this for my case presentation! thanks!