My 14 year old pit

I have a 14 year old pit named Bear. This year we have had alot of scares with him being sick. Well he has stopped eating for the most part and all he will do is drink water. He has had a few accidents, which have been increasing lately. He hasn't really deficated which is understandable since he hasn't been eating. Today he  finally went to the bathroom and is was mustard in color with a strong odor. It was not diarreah (diarrhea) but more soft then anything.
What is this indicitive of? Is he having kidney failure?? I know in humans this is indicitive of kidney failure at an older age. I have taken care of my mother in law when she was having renal failure and this is what she did so I am worried. I do not want my baby to suffer how she did.

[lindapalm]

Have you ever had his teeth checked by a vet?  That is one reason why dogs stop eating, possibly its why yours won't eat.  Also, the excessive peeing could be any number of things, I would definately have him checked by a vet.

[Margot49]

With the stool being that color, I would definitely take a stool sample into the Vet and have it checked.  A blood panel may not be a bad idea either.

[ginger899]

It's hard to say, but often when stool smells that bad it can be indicative of some kind of infection, or possibly food staying too long in the gut. And a yellowish colour can either be because of the colour of his food, or if it isn't that, it can mean a problem with the bilirubin levels in his liver. However these scenarios are manageable.
It may be none of these things. But take him to the vet. Like Margot said, stool sample and bloodwork.