Hello, I am Dr. Peter a licensed Veterinarian. I would like to help. I need to ask you a few questions to be well informed and give you the best advise. There is no additional charge for information request.
1- Besides blood work as your vet done additional tests like xrays or ultrasound?
2- Did they check if he is leukemia and AIDS negative?
Usually increases in white blood cells are due to infections; I would recommend you speak to your vet about starting your cat on a broad spectrum antibiotic; once the infection is under control then the WBC should return to normal. Your vet can look for evidence of infections through the use of ultrasound and checking both the chest and abdominal cavity. Less likely these increases in WBC can be related to an underlying tumor or problems within the bone marrow (area where WBC are produced) itself. Before looking into the bone marrow, it is important to rule out infections. If the blood work did not show which system may be the problem, this is when we need to use ultrasound to try to find it. I would recommend you speak to your vet about this approach.
If you have additional questions I will be glad to answer them.
When we see such elevations of WBC's it could be related to cancer, but, it can also happen with an infection. Depending on the type of WBC's that are elevated will give us a better idea if it is related to an infection or cancer. This is why I recommended a double cavity ultrasound; the veterinarian can look for either an infection like abscessation in the intestinal tract or they can find evidence of cancer. If they do not find either, then the problem may stem in the bone marrow and a bone marrow aspirate would be indicated.
I know this can be confusing, if you have additional questions, I will be glad to answer them. I will be online for another hour or so.
Your Welcome; Good Luck!!!