What Causes Swelling In The Feet And Calves?

Hi doctor, My age is 39 m weight 85 and hight 178.I have been on two days travel and have been travelling by bus. While back from the travel, I noticed that my feet and calf were swollen. I waited for two days but the situation remain unchanged. My doctor advised me to get some tests done. The report says SGPT as 61 and Hb as 11.30. rest all tests are withing range. Please advise.