['I hope you never have kidney stones, but I have had several.  A month ago, I had to have surgery because one was lodged and was too big to pass.']
Ouch, that sounds so painful!  No I have never have them.  Do you know you can avoid them in the future?
I recently had surgery for a kidney stone.  I am so thankful for my wife who took such good care of me after the surgery.  I was under her care for two weeks, but she was so considerate to all my needs.