Hello, my son had the same op at 12 weeks back in May so completely know how you are feeling at the moment.
Hard I know, but try not to worry. The op has a great success rate and I've noticed a big, positive change in my son since he had his. I've jotted down a few things that I thought might be helpful for you before Tuesday.
During the op: Go and get something to eat! We headed to a cafe across the road from the hospital and left our mobile with the team in case they needed to contact us. You'll be busy once your daughter comes out of surgery so it's got to get out of the hospital and take your mind off things, even just for an hour.
GA: My son's operation was about four hours from start to finish (his hydronephrosis is in his left kidney, no UTIs before or after surgery, but on daily antibiotics) and he coped really with with the GA. The first day/evening was a bit tough as the GA wore off, but the medical team were constantly monitoring him and had him on a regular dose of morphine- he had his op on a Friday afternoon and they stopped morphine by 9am Saturday.
Scar- My son has a little neat scar a couple of CMs-wide on his side. It healed super quickly - advantage of having the op so young I think in that recovery time is much quicker.
Bigger nappies/clothes etc - we bought in own nappies a size bigger as son had a catheter for first couple of days, and a stent too. The hospital was really warm so he lived in short-sleeved vest/rompers a size bigger than normal.
Toys- we brought in a couple of rattles and fabric books to try and distract him, and used those Milton wipes to keep them clean!
Feeding- my son is exclusively FF so I brought in a couple of bottles, travel cold water steriliser and some pre-mixed formula to store in the fridge, but when I arrived the staff had already set up a steriliser with bottles, dummies, and milk (they had SMA) which I used instead. There was also a hospital grade pump in case I wanted to express, and they encouraged breastfeeding too. Mum next to me was able to BF straight after her daughter was brought to the ward after a similar op.
Coming home- We were discharged late on a Sunday night after a member of the surgical team checked him and tied off his stent coming out of the op site - they tied a knot in it, coiled it round and put a clear dressing off it and the stent was removed in a outpatient appt a week after surgery. They weighed his nappies before letting us go home to check his urine output (!) and we were given a week-long course of antibiotics too. The only thing I wish I had done was listen more attentively/jot down notes on any poss signs of infection as I then worried that I was missing something when I got home. The staff were brilliant at explaining things if I was unsure about anything, so ask away if you are unsure too.
Our son had his op at another London hospital, but I found these guides from Great Ormond Street and Evelina Hospital super helpful:
www.gosh.nhs.uk/medical-information/procedures-and-treatments/pyeloplasty
www.evelinalondon.nhs.uk/resources/patient-information/pyeloplasty-going-home.pdf
Sorry for the huge post, but didn't want you to go unanswered. We've had one post op ultrasound so far and an outpatient's appointment next week, so keeping our fingers crossed that the op has done the trick. The only thing I would say is that the difference in my son's mood post op was remarkable- he seemed much calmer, more alert and happier. My FIL described it as a lightbulb being switched on. He's steadily put on weight, smiles all the time, feeds a lot better than before (we thought he had colic/reflux, but seeing the difference in his mood now not so sure!) and he was back rolling once his stent came out- and he was crawling at five months!
I shall keep my fingers crossed that all goes well for you on Tuesday- babies are amazingly resilient and I'm now grateful that he had the op at a young age so he won't be able to remember it. If you have any other questions, just post on this thread and I'll try and help if I can! Lots and lots of luck xx