White powdery substance?

[Truffle Risotto]

Hello, I posted a thread here before about my rabbit dribbling pee and getting his tail wet. We were able to find a good vet that checked him and found out that he had a mild infection, she gave me Metacam to give my rabbit 2ml once a day for 5 days and Chloropal forte to give 1.5ml in the day and in the night for 6 days. However, I noticed just before we took him to the vet a white powdery substance on the floor, it was just a bit but I've been seeing it very often now and I'm wondering what it is because I'm very concerned, I was thinking it was sludge, but I don't know. Thank you so much for your help. I've attached images of it.

 

[JBun]

It could be dried sludge from his bladder. If it is, then it would also explain the urinary problems he's been having. Which means if he still is continuing to have urine dribbling and other bladder issues, that you would need to get it checked at the vet.

If he seems fine now, what I did for my rabbit prone to developing bladder sludge was to keep him on a low calcium diet of low calcium grass based pellets, low calcium veggies/greens, and low calcium grass hay. Some people with bladder sludge prone buns also use low calcium bottled water. I also made sure he drank well as good hydration is important, and that he jumped up and down a lot to help keep any sediment churned up in his bladder to make it easier to excrete.
https://rabbit.org/lowering-blood-calcium/