Usually for live kidney donation they leave the diseased kidneys in situ as removing the kidney's is a significantly larger operation. You will find the donor has more discomfort post operatively than the lucky recipient.
I work in deceased donation- let's spare a thought this Christmas for the families around the world who have lost someone dear but who have given permission for organ donation to proceed and the thousands of lives that has saved!
These families have gifted life, sight and transformed lives of so many mothers, fathers, brothers and sisters and yet families sadly still often refuse when asked.