A. I am really sorry to hear about his condition. Steroids are a palliative treatment in this case, but the multi systemic disease will progress unfortunately.
Consider euthanasia as slow an gradual deterioration of his condition will severely affect his quality of life. I would recommend to discuss with your veterinarian about his quality of life going through a physical examination and considering the investigations performed.
I am happy, if you request a consultation (if you think it may be helpful), to discuss in details with you the tests done so far and his quality of life assessment.
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