swelling in the legs

I have completed 3 years of my 5xcabg.  Veins were taken from both legs  below the knees.  So far not much problems, but for the slightly uncontrolled diabetes.  Of late my feet are getting swollen, especially while sitting at the office. 

By evening it gets swollen pretty well.  By morning it is almost normal.  Can anyone advice regarding this problem

Regards