Dog acting down

We have a 8 month old Yorkie she was playful and ornry. My daughter got a kitten and the dog wanted to play with the kitten but was too rough with it. Now my yorkie lays around, wont eat, doesnt potty outside she will come in and potty on the floor. I am very worried about her, she doesnt act herself.

[Cliff Redford, DVM]

While this coincides with the introduction of the new kitten, I expect this is not in fact behavioral but is a medical issue. To say what though is too difficult. The possibilities are endless...viral, bacterial, inflammatory, toxin, etc. an examination is needed as soon as possible. Has she been spayed? It may have something to do with that.