Get Pet Questions Answered by Pet Experts
At this age, there can be a lot of cause including liver and kidney failure so you will want to rush to the vet to have the vet take a look.
You also have to remember that even at this age, they can are still succeptible to parasites and giardia and coccidia, both of which can cause bowel problems.
If you have not seen the vet yet, I suggest that you do so in order to rule out parasites as the cause.
Let me know if you have more questions.