I have noticed that he's been drinking a lot more lately; he also eats a decent amount, which is why it's surprising that he's losing weight.
drinking, good appetite, losing weight...my first reaction would be hyperthyroidism. You would need a free-T4 blood work. At least treatment would be pretty easy.
You might want to bring a urine sample (much less expensive than a blood test) to rule out sugar in the urine -is Jo overweight?, or signs of declining kidneys (low gravity and presence of protein).

We are right now also going through the same thing with our almost 14-year old lady (although her weight has been stable). So we are waiting for the blood results-not until Thursday.

If blood results show nothing, I certainly would go for X-rays.
My very best to you and Jo, and keep us posted.

Anne-Marie

anne_marie, they did get a urine sample out of him when he was there. I would assume that they're doing a free-T4 test with the blood they drew, as a matter of course? He's definitely not overweight -- he's always been fairly skinny, and now he's starting to look a bit gaunt. :(

Actually, for diagnosis of hyperthyroidism, the test you want is a Total T4, not a Free T4. It's not generally included in a standard blood chemistry, so you'll need to make sure your vet runs the thyroid test. Also, be sure to request copies of ALL test results - blood and urine - for your own records at home. You'll need them to do online research, ask for applicable advice on forums like this one, and to make sense out of what you learn.

Hyperthyroidism, diabetes, and chronic renal failure (CRF) are the three most common diseases in elderly cats, and each can exhibit the symptoms of excessive thirst and weight loss. A full blood chemistry, Total T4, and urinalysis will help diagnose or eliminate all three. All three diseases are manageable if caught early. HyperT can even be cured, and diabetes can go into remission in a lot of cats.

Let us know how the tests turn out.

Laurie

My cat was hyper-T twice (and had two rounds of radiation; he's fine now and we are keeping our fingers crossed!). Both times he lost weight quite rapidly: over a period of 3-4 months his back side got noticeably "pinched" in like a very old and sick cat. He was just ravenous for food. Rather than lethargic, however, he was increasingly agitated and irritated and howled often.

Got the bloodwork results back, and there's nothing abnormal. When I asked about thyroid testing, they said that it was included in the bloodwork, and appeared perfectly normal.

I guess we'll do an x-ray next, unless anyone has any other suggestions of what we should be looking for. But what could possibly be causing tons of drinking, that would show up on an X-ray?

If I were you, I'd want to take a look at all of those test results myself. I can't tell you how many times vets have told me that "everything looks normal", when, in fact, the bloodwork or other tests clearly showed some abnormal values. Sometimes even values that land within "normal" range can be misleading. For instance, a Total T4 can register in high normal range even when there is thyroid disease present. For that reason, I would do further testing after a high normal TT4 to clarify and verify thyroid function, esp. with your cat's current symptoms.

In any event, there's no harm in requesting copies of your cat's test results so you can see for yourself if everything is, indeed, normal.

Laurie

YES, indeed, Laurie is sooo right!! Get a copy of all the tests and you'll learn a lot. I had a vet who once told me that all the numbers looked good.. for an "older guy", she added. Wish I had seen those numbers for myself... As we all know, early detection is key.

Anyway, here are two links that will help you make sense of these numbers.
Understanding lab results
understanding your pet's bloodwork
lab tests

And, as for your question about X-ray,.. I would say that an X-ray will show abnormalities/ tumors with some organs (kidneys in particular). I'm not sure why the cause of extra drinking would not have showed up on the lab work, though.

Best of luck,
Anne-Marie

some additional thoughts about lab results concerning T4 levels. The normal range indicated by most labs is very wide, much too wide, even if a "grey" zone is also quoted.
Let me quote Dr. Hodgkins fron her book "Your cat".

"I have neever seen a Total T4 test result in a healthy cat, even a young one, above 3.5 micrograms/deciliter. On the other hand, the normal, healthy older cats I have tested always test below 2.0 micrograms/deciliter.
...No matter what the original T4 level, if the cat's thyroid hormone is increasing over time, then the veterinarian should be very suspicious that hyperthyroidism is present, because thyroid hormone levels in normal animals fall as the patient ages." --this is what I have seen with my 'old lady'. And this also tells you how important it is to keep copies of your cat's lab results.

Hope this helps,
Anne-Marie

Okay, I got them to fax me the bloodwork results. The T4 test result is 1.6, which does appear to be perfectly normal. All of his other results seem well within normal range (except for his cholesterol, which is 241), barring a couple of things in the urinalysis:

Protein: 1+ (HIGH)
Occult Blood: 2+ (HIGH)
RBC/HPF: 4-10 (HIGH)

I have no idea what any of that means. Think it signifies anything? His urinalysis results from 4 months were high as well, but fine a year ago.

The list of results is really long -- if you want me to post anything specific, let me know. I had them send over the past 4 sets of bloodwork (covering the past couple of years), and the only real difference I can see between the older ones and the newer ones is the urinalysis stuff. The T4 has stayed pretty consistent over the past couple of years (1.5 to now 1.6), so it would seem that hyperthyroidism is out.

I'd like some recommendations on what to do next. Get a second opinion? Go back to my vet and discuss the X-ray/ultrasound option? Any advice is appreciated.

I just did a bit of research, and it looks to me like those urinalysis results necessitate further testing. The link below will provide you with more information. Pay particular attention to the sections on protein and blood. Your cat's urinalysis results are definitely something you should discuss at length with your vet.

Here is a link that might be useful: urinalysis interpretation

I'll agree that HyperT is out.
For failing kidneys, the most important blood numbers are BUN, creatinine, phosphorus and calcium.
I believe that a slightly elevated cholesterol value is not an issue for cats.

Looks like some sort of infection. Hope your vet was able to explain the urine test results to you. The source of Jo's problems seems to be there...

Thanks Laurie for that great link. That will help me when I get my urinalysis results on Thursday!!

Anne-Marie

"leave him be" then (and leave your wallet be.. lol!)
Glad the X-ray did not turn out anything.
Hope he keeps gaining some weight, that's always a good sign!
Thanks for the update,
Anne-Marie

I have the exact same issue, anything you learn would help