Unknown health issue

Question
Hello,

I have a 6-year-old neutered mix-breed bunny. He was perfectly healthy up until last year, when I noticed that he had been losing weight. He also started urinating outside the litter box.  He was still eating, but not as much as before.  I took him to our rabbit-savvy vet.  The bunny's teeth were normal.  His blood work was normal (I thought for sure kidney issues would be indicated), and his x-rays were normal,except that his liver seemed smaller than normal.  I was referred to a different vet to take an ultrasound which also turned out normal.  I focused on putting some weight on him, and he gained some ounces back and the follow-up blood work turned out fine.  I did notice some subtle gait issues, and my vet prescribed a daily dose of panacur.  The panacur seems to help in the sense I don't see him sway when he sits.

He doesn't have trouble jumping into the litter box (and now I have a cut-out litter box too, so he doesn't have to make the leap in), and he'll use the litter box sometimes, but frequently urinates on the floor.

As irritating as it is to constantly mop up urine, I am more concerned about what may be possibly bothering him.  The vets cannot find anything wrong, but they do acknowledge there is definitely something off with him.

Do you have any ideas what may be going on?

Thank you!!

Answer
Dear Jody,

Boy.  The minute I came up with an explanation, your vets had it covered.  I thought renal disease.  Nope.  I thought dental problems.  Nope.  (Unless the dental check was done with bunny awake; for a really thorough dental exam, anesthesia is needed to get the mouth far enough open to see 'way into the back of the mouth).  I thought E. cuniculi.  Vet already got the Panacur covered.

So this is mysterious.

I do think that a really *deep* mouth exam may be warranted if bun has not been put under for a really good look.  Sometimes some pretty scary molar problems are not visible until the bunny is really relaxed.

If you're not sure your vet is a bunny dental expert, check the lists linked here for a referral:

http://www.rabbit.org/vet

The other possibility is bladder sludge or stone that are radio-translucent.  But that would be really unusual.  If he has a urinary tract infection, it will be difficult to culture, as pathogens that cause these are often obligate anaerobes and hard to get out of the bladder alive.  But if your vet can get a sample of urine and keep it cold, any pathogens could be identified with PCR and DNA sequencing (which is what most labs are doing these days, anyway, in lieu of culture and sensitivity).

I hope someone can find out what's going on!

Dana