Not sure how much you have read, but you should be drinking at least 2 quarts of just water a day, 3 is better. You want to be very well hydrated going into surgery and now is the time to start. You will also need to drink this much everyday after surgery to flush out your remaining kidney and keep it healthy.
Celery, cucumber, and fresh squeezed lemons are wonderful diuretics. You can slice all of this into a 2 quart pitcher of water and refrig over night. Drink through out the next day along with plain water to equal the 2 quart amount total. You might be running to the bathroom often, but it will really help flush the fluids from the surgery, especially with the TT you are also receiving. Or, squeeze 1/2 lemon into a cup of hot or cold water, sweeten with honey or sugar(stevia) and drink. Have at least a couple of these a day to flush the body instead, what ever works for you. You should also be upping your protein, at least 25 grams per meal, getting ready for surgery, and lots and lots of leafy green vegetables. I wish I had known these things prior to my donation so I could have bounced back faster. Hind sight puts it all into perspective.