My 11 yr old cat has been losing weight for three years. Lots of trips to the vet for diarrhea and occasional vomiting. Injections of cerenia and centrine seemed to help. Still my cat has kept losing weight. All the blood tests came back normal. Now I'm wondering if it could be IBD or cancer? My cat is still playful with energy so I'm wondering if it could be cancer for three years? Or something else. The vet suggested ultrasound but it probably would not be conclusive by itself. Any suggestions or experiences?