My Son Is 66 Yrs. Old. He Had A Very

My son is 66 yrs. old. He had a very large kidney stone that had to be removed several years ago. Very painful. This week he has passed several small ones and today he has felt on for the 3rd day and doesn't want to pass. He eats dinner with me about 4 times a week. Am interested what I can to do to help prevent this from continue to happen.