Cat not feeling well...advice needed!

[foogs]

My 15 year old, indoor, female cat has been drinking a lot of water, sometimes to the point where she will throw up. I have also noticed loose stool (twice in the last two weeks), stomach gurgling as if she has gas and she has been sleeping a bit more than usual. Before bringing her to the vet I researched online and it looked like she had the symptoms of Chronic Renal Failure (CRF).

Fearing the worst I brought her to the vet to have blood work and a urine analysis performed. The blood work came back with everything normal. The vet actually said that it looked like the blood from a three year old cat. The urine analysis that I collected at home myself came back today and it had a high PH level as well as crystals. He put her on an antibiotic (Clavamox) for two weeks and a Science Diet C/D diet. I feel like they are missing something given all the symptoms.

I'm currently speaking with a vet using the justanswers.com website and she feels the vet misdiagnosed the struvite crystals because crystals supposedly form in urine within five minutes of sitting outside the body and crystal development in a 15 yo cat would be very odd. She looked at the blood work results and agreed that it looked good, but said the results don't mean much without a 'urine specific gravity' (USG) reading (I never heard of this). She feels it may be kidney disease, a kidney infection or a bad bladder infection.

If anyone has had any experience like this and wouldn't mind sharing your thoughts or your story I'd really appreciate it. I'm looking to get as much information as possible. Thank you.