>>510467962 (OP)It's called edema and it's when fluid builds up in some part of the body. The feet and lower legs are common places for edema, as is the chest cavity around the lungs and heart and even in the skull around the brain.
There are medications that treat edema. Basically, you go pee a lot to expel the excess water.
Edema is very common in the elderly, sort of a chronic issue that they have to treat from time to time.