Bladder sludge

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My rabbits live outside and their house connects to the shed so they can enter a warm place at night. Just today,I noticed that they moved the litter box and peed on the floor of the hutch it leaked through and now I see the puddle of the calcium excretion (I usually see and wash away)today there was a puddle of brown liquid surrounded in the calcium is this bladder sludge or normal urine...

 

[Blue eyes]

Here are some photos to use to compare:
http://www.medirabbit.com/EN/Uro_gen_diseases/generalities/Sludge.htm

 

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Here are some photos to use to compare:
http://www.medirabbit.com/EN/Uro_gen_diseases/generalities/Sludge.htm

Thank you so much ....I’m still having some trouble

 

[:))]

Here are some photos to use to compare:
http://www.medirabbit.com/EN/Uro_gen_diseases/generalities/Sludge.htm

Here’s an image