lisamgoldberg,
My surgeon told me I had a minor, theoretical, problem with my left kidney. I asked, "So, you will take my right kidney, correct?" "No," he said, "we always leave the donor with the better kidney." The reason is that they want to minimize potential harm to the donor.
BTW, usually a person's smaller kidney has a lower level kidney function than the person's larger kidney. But not always. The nuclear dye test will determine which kidney has a higher level of function.
I believe that most -- if not all -- programs take the kidney that is less good, and leave the better kidney in the donor. In any case, you can refuse to have the surgery if the program wants to leave you with the less good kidney. DO NOT HESITATE TO PERSIST IN ASKING QUESTIONS, & GETTING THEM ANSWERED TO YOUR SATISFACTION! [I say that as a physician.
] It is your life, after all!
Bill