Research regarding kidney failure: I´m perplexed

Last night I was watching Animal Planet when I learned that reseachers
are studying the biochemistry of polar bears because they may find
something that may be beneficial for kidney failure patients.

This is what got their interest: polar bear will hybernate during the
winter without defecating or urinating.

What I know regarding polar bears is that they will gain a lot of fat
during the warmer months to be able to withstand hybernation. When
food is abundant, he will eat mostly the fat and leave the meat and
bones behind.

Now here are my questions:

If one does not eat, one does not defecate. If the polar bear is not
eating during his hybernation, why should he defecate?

Burning fat will result in carbon dioxide and water. Carbon dioxide is
eliminated by lungs and water is also partly eliminated by lungs. The
bear is not drinking water during his hybernation so there is no real
need to urinate. Fat, unlike protein, will not generate urea.

Did I miss something or are they waisting time and money with
something stupid?