urine sample

Is having crystals in urine the same as sludge please? I can't find much about having crystals. Has anyone had a piggie with crystals? Nancy has them and I think that maybe why she keeps squeaking in pain.

I had the pigs at the vet tonight because Toast has put on quite a lot of weight over the space of 2 weeks, despite absolutely no changes of their diet, I've not fed them more or anything new so there's no obvious reason to put on weight. I always watch them eat and finish their veg and there's...