First, I am glad to see that you have wormed him, since while it didn't address this for him, it does allow us to rule them out as a cause for his signs. Now as I am sure you can appreciate fecal urgency with increased GI pressures (after eating) in cats with diarrhea
can be caused by a range of conditions. This includes low grade bacterial or viral agents, parasites (worms
that you treated for but also protozoa), inflammatory issues (ie IBD), and unfortunately we can also see this type of situation with some cancers (ie GI lymphoma).
With all this in mind, we do need to approach these situations with a step-by-step approach. Now I know you are not keen for invasive testing. Still, I would note that it would be worth considering submitting a fresh stool sample to your local vet (or to the local vet lab if they will accept samples directly from the public as some will). Often you don’t even need to take a cat in to submit one. Why this is ideal to have done at this point is because it can be tested for viruses, protozoa and parasites to rule them out or let you know if one is to blame. As well, the sample can be cultured for bacteria and it can be determined if one is to blame for his loose stool and what drug it is sensitive to. Of course, if they did find something that needed antibiotics or specific prescription treatment, then we’d need him checked but it would allow you to avoid invasive testing while helping him. And I do have to note that if it was completely normal, then we’d have to consider those last concerns (which could warrant further testing but you could speak to his vet about using palliation like steroids instead of doing so).
Further to determining that root cause for his signs to see if we can address them, I do want to note some supportive care that could help here. While diet isn’t likely the main reason for his signs, I would note that we can see the use of sensitive stomach diets (ie Royal Canin Sensitivity Control or Gastrointestinal, Hill’s ID, etc) be useful in these cases. This is because they are easy to digest, so it means more nutrients in, less diarrhea, and therefore less weight loss. Since diarrhea can often cause dehydration, you could aim to feed a wet version of this type of diet. And just to note if you did, you could also add a fiber supplement (ie a spoonful of tinned pumpkin or ¼ tsp of unflavored Metamucil) to his diet to bulk up his feces and give it more form (and thus help him have better control).
As well, while you have wormed him already, I would just note that it'd be worth double checking what wormer you use. If it wasn't Panacur or one that contained Fenbendazole. Then I would suggest that it is worth using this. The reason is because it is a good wormer but also does help some of our protozoa (not all, but it would again help us rule some of the more common ones).
Another supplement that would be worth considering her is a feline probiotic. Often when the gut is under attack, we see the good bacterial population of the gut struggle (which isn’t ideal since they are what help us digest and produce normal stool). So, you can also use an over the counter probiotic (ie Fortiflora, Protexin Enterogenic) to help restore the normal gut balance. This is available in pet stores, vets, and even online (ie Amazon).
As well, I do want to note that there are cat safe anti-diarrheals that you could also try with him. It won’t cure the cause for the diarrhea, but it will reduce its runniness, give it form, and give him more fecal control and chance to absorb as much as possible. In regards ***** ***** options, the one we most commonly use is Kaolin/Kaopectate (More Info/Dose @ http://www.petplace.com/article/drug-library/library/over-the-counter/kaolin-and-pectin-kapectolin-k-p) available from your local pharmacy. As well, there are Kaolin + probiotic treatments for vets that combine these last 2 and could help. In regards ***** ***** there are a range you can use (ie Fast Balance, Protexin Pro-Fiber, Propectalin) and again we can get this OTC at vets, pet stores, and online at places like Amazon. So, these would all be options to use to slow that diarrhea and at least reduce his accidents and weight loss. (Though just to note, do avoid Pepto Bismol (as it contains aspirin) or Loperamide (since this can be toxic for cats)).
Overall, we do have a number of considerations for this diarrhea. Still, I would advise the above for your lad. This will help us pinpoint whether there is a treatable issue afoot, while trying to help control that loose stool for him. Hopefully, we will just find a bacterial or protozoal agent that just need treating but the above should also help get him more comfortable generally and try to reduce these severe diarrhea based accidents.
I hope this information is helpful.
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All the best,
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