Q. My 13lb dog has had diarrhea for 2 days with a lack of appetite but she is fine otherwise with no fever or any other symptoms.
DR. CHRISTIE LONG, D.V.M., C.V.A.
A. Lots of things could be going on in your dog. At 7 years old and as an unspayed female she is in the prime age for a condition called pyometra, in which the uterus gets infected. It's very serious and requires emergency surgery. Often they don't show any big signs that they're sick. So if for no other reason that that, I would get her checked out, and if it's not pyometra I would strongly recommend you consider spaying her to prevent this condition in the future.
As for the diarrhea, if she's not developing pyometra, it could be related to a number of things, including parasites, eating something that didn't agree with her, a sudden change in food, or more serious things. If it doesn't resolve after 24 hours, or if she starts to show any other symptoms she should be seen by a vet.