sludge

My rabbit is a 3 year old mini-lop, today I found what looks like a white stone in his litter tray, is this a bladder stone? Is this something to worry about, should I take him to the vet? He doesn't seem sick and is acting quite normally. Not sure how serious this is...help!

Hello! My baby Marshmallow has sludge in his urine and hasn’t been wanting to drink water. He was at the vet the other day and all his vitals, bloodwork and exam were normal other than the sludge. I tried to encourage him to drink more water by putting some apple juice in his water but he...