Bunny question

Question
I have a m/n mini lop.  He is about 4.5 years old.  Just recently he has started urinating and defecating out side his litter box.  I brought in a urine sample and everything was normal, except it indicated he had struvite crystals in his urine.  The vet I take him to said this is the first time he has seen struvite crystals in a bunny and he didn't know how to interpret it.  But he said there was no infection or anything so he thinks it might be behavorial.  So I tried changing his litter box.  He did not like the new one.  I scrubbed out the old one and cleaned it up good.  And I started putting his hay in a box.  But now he is going in his ltter box and his box with the hay.  I let him have free run of the living room.  I have a cage base that I keep his litter box and food box in.  I'm wanting to change the litter box base to a new base, but can't find one that is lower and big enough for him.  any suggestions for a new base? and any reasons why he would decide to start going to the bathroom outside his litter box?
Thank you

Answer
Dear Leslie,

Is the vet you saw very familiar with rabbits?  How did he identify the crystals as struvite (ammonium magnesium phosphate), which are relatively common in dogs, but not in rabbits.  In fact, I've never heard of struvite in rabbits.  

On the other hand, calcium carbonate and calcium oxalate crystals are *very* common in rabbit urine, as they excrete excess calcium as salts via the kidney.  If your vet wasn't aware of this, then you might want to find another vet to treat your bunny.  You might be able to find a good rabbit vet here:

www.rabbit.org/vets

though I'm told that they are--unfortunately and inexplicably--few and far between in Canada.  :(

And no, I don't believe that sudden loss of litterbox habits in a 4.5 year old rabbit is just a behavioral problem.  If he's not neutered, that might be a factor.  But it is more likely that he has a urinary-tract problem, or possibly another health problem that's making it hard for him to jump into his box (arthritis or other source of pain).  Please see:

www.bio.miami.edu/hare/urinary.html

for more information on some common urinary tract ailments in rabbits, and then you'll be better armed to ask the new rabbit vet about what could be going on with your bunny

I hope this helps.

Dana