Drnee has covered the mechanisms very well. You need a good work-up.
That being said, one of the best treatments for such swelling was standard medical practice a hundred years ago and has been forgotten.
That solution is great-great-grandpa's rocking chair!
Physicians in the 1880's would prescribe regular daily workouts on the rocking chair. As your legs "push" back, the fluid is forced upwards.
Talk with your doctor about treatments, which may include diuretics, generally lasix (lasts "six" hours), a compressing elastic stocking (don't get one too tight!), and elevating the foot/leg.
Vitamin C, in larger doses (1000mg) is a diuretic, and will act in the same way as lasix, although less effectively. Don't take more than 1000 mg because you will probably end up with loose stools.
Hi
Thanks for writing to the forum!
The swelling of feet could be due to water retention as in low protein in blood, kidney problems, severe anemia etc. It could be due to hypothyroidism too. Diabetes Mellitus too can cause similar symptoms. The diagnosis and further tests will depend on whether the swelling is a pitting edema (causes a dent on pressure) or a non pitting edema.
You can refer to this link for a complete list of possible causes for ankle, leg and feet swelling: http://en.diagnosispro.com/differential_diagnosis-for/bilateral-leg-edema-swelling/39352-154.html
I think you should discuss this with your doctor. Also you may need to get some tests done. It is difficult to comment beyond this at this stage. Please let me know if there is any thing else and do keep me posted. Take care!