Hi! My 3-year-old pig (Nacho) had two calcium stones in his bladder that were causing him some extreme pain. When we got the x-ray results showing the stones, we thought we'd have to do the risky surgery.
However, we wanted to try a different way. We got one of those water syringes that you can use to clean your wounds after wisdom teeth removal surgery (I have attached a photo of one to this post. It only costs a couple of dollars). We used this syringe to give him one syringe-full of water 1x/day.
A few days later, we actually found the calcium stones in his cage! I'm sure it was painful for him, but he was able to flush them out naturally and now he is perfectly fine. We now continue to syringe water to him once every 2-3 days.
Hope this helps!