Kitten with swollen lymph nodes...vets stumped

Here's a bit of history on the little guy:

He was born in March & pulled from a high kill shelter a few days after birth.  He was in a foster home with his siblings and no other cats but was brought back to the shelter for some amount of time the day I adopted him.

He was dewormed/combo vaccinated around 8 weeks

I adopted him in June

I had him dewormed/combo vaccinated around at about 12 weeks

He tested positive for coccidia after having loose, smelly stools & some watery diarrhea.  He was treated with Albon for 10 days.  This was at around 13 weeks of age.

I brought him to a walk-in clinic when I noticed sneezing & a bit of a runny nose.  The vet brought up the possibility of FIP, which I've lost a kitten to a few years ago.  He didn't think it was a big possibility & kitten did not have a fever(taken at least twice now on different occasions).  He suggested I treat him with Revolution & give him children's Benadryl(to rule out allergies).  I treated him with Revolution & Benadryl, though I'm not sure how much actually got into him as the flavor made him foam at the mouth..

I didn't see any improvement.  Still sneezing & smelly, loose stools here and there.  We returned for our next visit later that week..

About a week ago he put him on Clavamox & something for GI symptoms(chalky white stuff, name escapes me).

Our last visit was yesterday & the vet suggested putting him on Hill's PV, which I left with, and coming back when his Clavamox runs out.  His sneezing has improved & I haven't noticed URI symptoms.

I'm at a loss as to what to do and have just been following this vet's advice as so much of my energy is focused on my geriatric cat right now.  The kitten was slowly introduced to my cats after his coccidia treatment & we had gotten to the point where he was draped across my oldest cat & one of my younger boys; it was precious.  However, the walk-in vet felt I should isolate him.  After the last appointment, he said it was okay for them to be together. 

I'm leaning towards bringing him to one of the vets I've seen for a second opinion but I'm also wondering what I could do next on my own.  The fecals were all in-house; should I request something more thorough?  He's been on probiotics but is now obviously on Clavamox so I doubt they've had much of a chance to "work their magic."  I had him on strictly NB venison & green pea wet for about a week without improvement.  He isn't running to the litter box having watery diarrhea; he goes about twice a day and it's always very smelly(to me, at least, as my adult cats are mostly raw fed - lower odor) and sometimes "cow patty-like"(vet described it as "clay-like").  I'm wondering if he's just been on too many medications & too much change for such a young kitten. 

I have the prescription diet allergy diet but I'm leaning towards returning it.  The vet wanted me to start him on it, then return in about a week to see if he's improved.  From what I've read, it takes much longer to determine whether he has food allergies or not.  I've been through food allergies with cats(two of whom I have now) and they had much different symptoms.  The vet felt he was young for them, along with being too young for IBD, most likely.  I'm worried he will develop long-term bowel issues if I don't tackle this now.  

So much for keeping this short!  I'm open to any suggestions for further testing or things I could try.  I lean towards feeding him a variety of foods and going a natural route with treating his loose stools(pumpkin, probiotics, enzymes).  I'll be going back to the walk-in vet next week but will probably also schedule with another vet.

Another note: my kitten is a smoke but I've noticed some white tips that look like a fever coat in recent days.  I asked the vet if he felt he had a fever coat and he had never heard of fever coats.  Is this something most vets know about?  I know it's generally something kittens are born with but I have had my adult siamese develop one before he had major dental surgery.

Edit: I completely forgot to mention his bloating.  One reason the vet brought up FIP was that his abdomen was distended.  Currently, I'm only noticing him bloating up after eating.  I have also smelled gas and his stomach was quite noisy for awhile but that has actually seemed to calm down..

I would have him retested with a fecal float for common parasites and also request the PCR diarrhea panel be done to rule out tritrichomonas foetus.  That will only be picked up on the PCR test. 

The clavamox could be contributing to the diarrhea as that's a side effect of antibiotics.  Sometimes it also causes kitties to throw up.  Gas is a common side effect of parasites.  Could also be food intolerance, but I would check parasites first and then work on the food second.

Thank you. This is exactly what I did & we should have the results Monday.

He's off of Clavamox now & I'm continuing to add probiotics to his meals. I really hope he doesn't have long-term GI issues; I have faced them with other cats and they're heartbreaking & frustrating.

How's he doing?  Hope you get some good news from the vet on Monday!

He continues to have some very soft, smelly stool, gas, and bloating here and there.  That aside, he's doing well.  The PCR panel was "negative for everything."  I'm a little worried that I should have waited until he had been off antibiotics for a couple of weeks but the vet assured me it wouldn't be an issue.  I'm giving him probiotics and hoping for the best at this point..

We just got back from the vet a little while ago and I'm feeling pretty distraught. I/one of the vets knew my kitten had swollen lymph nodes on his neck at one point but tonight it was confirmed his other lymph nodes are swollen as well. He was taken to the back to be retested for FeLV and fortunately he was negative.

He had very mild URI symptoms(sneezing) awhile after I adopted him, along with diarrhea here and there. He was tested and treated(Albon) for coccidia. He was given a two week course of clavamox. His symptoms today include gas/bloating after meals, stools that are formed but on the softer/smellier side, and of course the swollen lymph nodes. Oops. Accidentally hit "submit" when I got up to help my oldest cat. Will edit this again.

He's had a PCR diarrhea panel, multiple fecals in-house, his mom was tested for FeLV/I had him tested twice now, he's never had a fever when checked, and he has a massive appetite(but so did my kitten whom we lost to FIP, up until the very end). FIP has been brought up. Today the vet gave me a pack of Clavamox and said "it's probably some sort of systemic infection."

I'm leaning towards bringing him to another clinic for more opinions/tests. But I don't know what else to test for at this point. The vet didn't feel basic bloodwork would be helpful.

Any suggestions are appreciated.

A second opinion is a very good idea. Not all vets are created equal, and swollen lymph glands could mean more than a systemic infection. Good luck to you.

I'm not sure if I mentioned it in my original post but.. I had noticed his lymph nodes were swollen on his neck.  Today the vet confirmed his other lymph nodes(at least the ones on the back of his legs) were swollen as well.  He tested him for FeLV again and he was negative.  I was sent home with more Clavamox.  The vet couldn't think of any other tests to perform. 

If anyone has any suggestions for further testing(imaging, blood), please let me know.  I will be bringing him to a different clinic for another opinion. 

I would seek a second opinion. In the meantime, I suggest that you sprinkle a probiotic into his wet food. It will help with gas and bloating.