12 year old, 15 kg (30lbs) mutt, diarrhea (no blood) for last 4 days, not eating or drinking anything, vomiting if fed. Is on her estrous cycle. Fever. Leukocytosis with neutrophils. Mild anemia. Raised Creatinine and BUN. ( Mild Azotemia). What antibiotic do you recommend? What type of IV fluid do you recommend?
Diarrhea has many causes and they do not always require antibiotics. Antibiotics and IV therapy should also, only be given at the discretion of a veterinarian has given your dog an exam. The reason is that diarrhea can be caused by many causes, many of which are not infectious. Also, diarrhea may be primary or secondary. A primary cause where the infection is directly related to something with the digestive tract or a secondary cause where it is due to metabolic problems or a number of other causes. Here is an article on different causes of diarrhea that may be helpful: https://www.vetbabble.com/dogs/questions-dogs/why-my-dog-has-diarrhea/
As you can see in the article, you definitely need to have your dog seen by a veterinarian, as I am guessing that is how you have the bloodwork. The fact that your dog is not eating or drinking anything says that he is not feeling very well at all and I want to emphasize how important it is to talk with your veterinarian about the case and discuss the causes.
The rest of this post is to talk about the bloodwork, but I want to emphasize that this is not advice and just talking about what the bloodwork patterns mean as looking at your bloodwork alone, it is not enough to give a valid diagnosis. This needs to be done by your veterinarian.
Leukocytosis and elevated neutrophils can be caused by stress or infection as talked about here with leukogram patterns: http://eclinpath.com/hematology/leukogram-changes/leukogram-patterns/.
As for the other results, elevated Creatinine and BUN could be a result of dehydration secondary to diarrhea, but without knowing the degree of elevation, it is difficult to tell. A veterinarian should be able to check the urine’s concentration to ensure that the kidneys are properly concentrating the urine.
Minor anemia may be useful in helping find a diagnosis, but it depends on a lot of factors and there are many potential causes of anemia: https://www.akc.org/expert-advice/health/anemia-in-dogs/
Again, given your dog’s age and the severity of signs, it is important that you work with your veterinarian to ensure your dog is as comfortable as possible and to help you find the diagnosis and treatment of the disease if it continues.