Jaybay is correct.....This could be a number of things.....In a 9yr. old small breed dog; I'm thinking Collapsing Trachea, which is very common. Also, heart disease needs to be ruled out as this is also common in a small 9yr. old.....Your Vet needs to test further on both of these things.....And Yes, they are both treatable.......Let us know what happens & good luck........Karla
Sounds like you need to go back to the vet. It could be anything from allergies, to a respiratory infection, to something worse like congestive heart failure. The diarrhea may or may not be related. One thing is for certain - you won't know what it is until your vet examines him.