Lucy and weight loss

[Lernermichelle]

Since a little before her bladder stone surgery, Lucy has been steadily losing weight. She went from 9.6 pounds about 3 months ago to 8.4 pounds today.  The only problems I am aware of are that she had the bladder stone, and that switching diets to accommodate her urine problem and keeping her on Baytril for a month caused her to have very loose stools (there is sometimes form to them, so not exactly diarrhea).  She does not seem to like what the vet put her on very much (K/D dry for ammonia urate stone, which is a rare kind of stone), so she may not be eating as much (she has it free feed so it is hard to tell).  She tries to get the other cats' dry and wet food and wants to eat it, but I keep it away from her because of her bladder and loose stool problems.  She seems very happy, energetic, and playful, and not at all sick (knock on wood), and her blood work has been good.  But I am concerned about the continuing weight loss, and gave her Nutrical just now even though I am not supposed to due to her diet constraints.   I am working with the vet to find a new diet for her. This is my question to the group:  would you just assume, if you were me, that the weight loss is due to the diet she is on and that the loose stools are from the Baytril and diet changes (it started the day after the first diet change, but has not gone away except when given Diarsanyl) and just work to find another diet, or would you be scared it is something else like intestinal lymphoma or IBD (loose stools and weight loss can be symptoms of those)?  Those of you who have had cats with intestinal lymphoma or IBD-- have your cats been energetic and happy and wanting food (she wants what she can't have) and had loose stools and weight loss as the only symptom, or have they also been draggy and had lack of appetite?   Lucy has also had unexplained weight loss twice in the past and then regained all the weight.  But I think she now weight less than she did either of those two times. She is 8.4 pounds today.  She has been up to 10.5 at times in the past, though not for a year or so.   Thanks, Michelle