Any ideas

I have a 16 year old cat who became sick 3 weeks ago.  He was not eating, had diarrahea, walked like he was intoxicated, nails grabbed the carpet, and all he did was sleep.  We took him to the vet and she ran a gammet of blood work - which all came back normal except a tiny bit anemic.  His urine came back fine and he did not have HIV.  She gave us an antibiotic and sent us home.  2 days later when no improvement was noticed I took him back to the vet.  She x-rayed him and he had fluid on his lungs.  She drained the fluid which was milky and tinged a little orange/red.  After the draining, she took another xray and saw that he looked healthy.  His heart was good, no cancer or tumors that she could see.....Took him home and nursed him back.  He is now eating, but not even close to his former mouse catching glory (mind you this was 3 weeks!!)  The vet called and said that the fluid from the cats lungs did not test for bacteria.  She does not know what is wrong.  Any ideas would be great, I love cat!

[zodiacqueen]

Well, if a lung problem has been ruled out, then I'd get a more thorough investigation of the heart.  That's a great sign that the x-ray doesn't show any enlargement of the heart, BUT there is a reason that fluid showed up in the lungs...and this most definitely needs to be looked into.  I'd get a possible echocardiogram of the heart to see how it's functioning, and while they're doing that have the entire abdomen checked out with ultrasound.  Ask your vet about getting the ultrasound done, I bet he/she would agree that is your next step.  This really is worth looking into, especially since this is NOT a bacterial infection.  The ultrasound will give you a bunch of info on all of the organs-kidneys, liver, heart, etc.  The liver and kidneys do not show up on the x-rays.

Good luck to ya, and please post an update!!!