Original image URL: http://www.flickr.com/photos/emdot/14803556/
Title: Chapin at the vet.
Anyways, what does ADR stand for you ask? ADR stands for "Ain't Doin' Right". Yep, you read that right. This super fancy term is something used to describe pets who are most likely vomiting, have diarrhea, not eating, losing weight, and/or lethargic. I wouldn't necessarily call it a diagnosis though.
When a pet comes into the hospital with symptoms like the ones noted above, technicians may notify the doctor that the patient is ADR - along with describing the symptoms more thoroughly of course. Veterinarians may even write this in their medical records. If the pet's condition is a little harder to diagnose, they might claim that it is ADR until the mystery is solved.
This acronym is probably used on a daily basis in many veterinary offices. There wasn't a day that went by where the hospital I worked in did not see an ADR pet. Next time you are the vet's office and they ask what is wrong with your pet and you don't know (Which I hope never happens!), just tell them he's ADR. They'll probably understand.