I adopted my kitten from a shelter when she was three months old, and she has always had GI issues since I got her. I took her to the vet the first week I got her because I was concerned that she was vomiting, having inflamed lymph nodes, and having diarrhea. We tested her stool for everything-- the only significant result was low Giardia levels. Over the last year, we treated her with EVERYTHING: two rounds of metronidazole, a strict only-rabbit diet, pumpkin, psyllium husk, 3 different brands of probiotics. I was going crazy having to bathe her 2-3 times a week and chasing her down to wipe her butt because her loose stool would make a mess. This was the only thing that has worked. So far she has been taking capsules for about a week and her bowel movements have been perfectly formed. I am hopeful that this is the end of her GI problems. These capsules are expensive, but 100% worth a try. After months of trying solutions that only temporarily worked/didn't fix my kitten's GI problems, this is finally the thing that has changed everything!
Also, the capsules are very small and not a huge issue to administer. It can be a little distressing getting started with it, but the burrito method and placing the capsule quickly at the back of her throat has been working well.