Soft yellow stools and weight loss

Sorry that this is long, but I want to give ALL details in case it helps.

I adopted Plushy about a year and a half ago from a shelter. The shelter had said he was about 3.5, so my estimate was that he was about 5 years old now. He was never a very active cat, but would run around with our other cat at least once every couple days. In late October, he started having some cold symptoms (sneezing a lot, especially while eating) and was hiding under the bed more. Thinking he was a young cat, I chocked it up to being a cold and waited it out. After a few weeks, his cold symptoms were much better, but I noticed that he had lost some weight and was still lazier than usual.

I took him to the vet and was told he may be more like 9-10 years (the vet admitted it is very hard to tell, but by looking at his teeth and eyes, he thinks he is older than 5 but we cannot be certain of his age). In August when we took him in for his routine shots, he was weighed in at 10 pounds and the vet (same vet both times) didn't seem to notice the discrepancy in age, but did comment that a dental may be something to think about but he didn't think it was urgent (this will be more relevant later).

When he went in in October, he was 8.25 pounds. The vet figured he was hyperthyroid so we did a CBC, T4, Kidney, Liver and Chem Panel. The vet called and said his results came back "quite good" (I can post the numbers if you think that is helpful) and ruled out any serious problems as far as what the blood tests reveal. We put him on antibiotics to see if maybe the weight loss was from a URI or something, but that didn't help. We did fecal tests for parasites and also checked for giardia and cholitis... all negative. BTW: his stool is consistently a light goldish brown and runny, but the vet keeps brushing this off.

The vet decided the next step was to try separating his food in a different room since our other cat is much larger and seems to dominate the food (although this never seemed to bother plushy for the first year and a half we had him). While Plushy has been more cuddly again lately, he is still very thin (I can still feel his back and hip bones very easily). The vet said if he doesn't improve, we could test him for FeLV/FIV or do some x-rays. The paperwork I received from the shelter says that he was tested (negative) for FELV/FIV about 6 months before we adopted him and was current on all shots. He wasn't vaccinated for FELV and the vet seems to think this might be the answer but I have my doubts since both of our cats are indoor ONLY.

Plushy has been eating and drinking the entire time, although it may be a smaller quantity-- it's hard for me to remember because I only really paid attention when this all started. I have noticed that he seems to chew very deliberately (kind of like he is trying to chew with his back teeth... his mouth opens and closes very wide) and constantly drop pieces of food out of his mouth on the floor. It takes him a long time to eat compared to our other cat. Very recently (last week or so), I also notice that Plushy hasn't been eating as much of his hard food, but eats his soft food and still begs for people food so I feel his appetite is normal. I am starting to think this may be a dental problem, but the vet hasn't even suggested this.

Please let me know what you think this could be and what course of action for testing may be appropriate.

Thank you for your time and thoughtful answer. So should I rule out a dental issue at this point?

Thank you Dr. Marie! I am taking our other cat to the vet tomorrow to get his shots. I will ask about the possibility of trying steroids with Plushy for a short time to see if that helps. I have been doing some reading about use of steroids in cats and it says that it should not be used for prolonged periods. How does this work with a chronic disease like IBD? Is this something that he would have to be on for the rest of his life and if so, what is the prognosis for cats with IBD? Is it typical for a veterinarian to prescribe a trial dose of steroids without actually doing the biopsy?

Thanks again for all of your help!

Hi Dr. Marie,

Thank you again for all of your advice. He was tested negative for FeLV, FIV and Heartworm :) The vet did agree to put him on prednisolone for a trial and he was put on Hills I/D food. This is the fourth day he has been on the medication. How long does it typically take to see some changes if this is working?