I'm sorry this is turning out to be so drawn-out and stressful. If only the little darlings knew what they put us through!
Sometimes crystals are just caused by a pH inbalance in the urine; it doesn't always mean stones. I expected stones when one of my pigs had actual visible crystals, but it was just a case of the urine was crystallising due to a simple urinary infection. Baytril cleared it up for him as it was so mild, but I found other ABs do a better job.
As Caviesgalore said, avoid high calcium veg. Carrots, kale, parsley and spinach are most notably high in this, as are most herbs like dill, basil and mint. Coriander is about the best herb nutritionally speaking. Since excess calcium is eliminated in the urine, it goes through the bladder, and pigs with bladder issues tend to have a flare-up if too much excess calcium is in the system.
Some vets prefer to operate immediately upon the xray results; the pig already being anesthetised for the xray, it's better to get the surgery out of the way while the pig is out of it, instead of waking the pig and and putting it under again. The vet will ring you as soon as he has the xrays and ask for your permission, if immediate surgery is what your vet chooses to do.
Surgery should be relatively "straight forward" provided you have a very knowledgeable and skilled vet. The right anesthetic (no injectable), surgical suture and the right post-op care are usually the areas that, when done wrong, cause problems. When done right, the pig has received the best medical attention possible and the pig has the best chance at recovery. The majority of pigs do recover from this surgery just fine, but it doesn't make it any easier when it's our own pigs having to go through it.
Keep us updated. xx