My son has kidney problems as well - but was mostly a daytime wetter - whereas my daughter who is ADD - is a nitetime wetter. We used the alarms as well (waste of money in my opinion). Though this is what I've done - hope this works for you.
My daughter takes medication now to control her nitetime wetting - she takes DDAVP and Ditropan. What meds have you tried?
I don't allow any fluid intake after dinner and also no eating after dinner - eating promotes drinking - drinking promotes wetting.
NO soda's or sugary drinks. Water is always best.
Make sure she goes to the bathroom before going to bed and if she's still awake for a bit after going to bed - make sure she goes again - even if she says she doesn't have to.
Due to my son's kidney problems, I bought him a watch that he programmed to go off every 2 hours to remind him to go to the bathroom. I even went as far as getting a doctor's note to let the school know of his problems so that he'd have no problem getting up whenever his watch went off and just going to the bathroom without 'flack' from any of his teachers. You can do the same with any type of watch that has an alarm feature on it.
Another thing I've tried is going for acupuncture through the chiropractor. It did work for some time, but my daughter didn't like getting the needles any longer - so we stopped.
Whenever she does go to the bathroom - she should sit for about 3 minutes - if not longer - to allow her body to 'relax' enough to go. She may feel like she doesn't have to go - but if given enough time to relax... she should be able to go. I know this may not be possible to do during school, but if the school is aware that she has this medical problem - there shouldn't be a problem with her sitting there for 3 minutes.
Again - these are things I've used - and they've seemed to work. My daughter still has her bad days - and my son has stopped wetting his pants during the day.
Good luck - hope this helps!