Hello,
No it is absolutely not unrealistic. When we get feral cats at our shelter we try to treat them as best as we can, too. Obviously there are things that you can’t do with feral cats like you can with tame ones. But still we were still able do give daily fluids and feed them with a syringe, when they wouldn’t eat on their own for most of them.
However for this it helped a lot that they are usually in large crates, as this makes daily handling a lot easier. We place them in pillow cases to feed them or give them fluids. Most stay calm when they can’t see.
Also, a lot of needed exams can be done under anesthesia. Ultrasound (except heart), xray, bloodwork, urin analysis…
Not all treatments can be done with ferals, but there sitll is a lot of possible. That also depends on how far you are willing to go, and how stressfull daily handling for him would be. Most, while obviously hating to be forced daily, were still able to build trust after treatment or even with ongoing treatment. However it is helpful to have a second person do to the “bad” things.
Constipation in cats is usually secondary to another issue. That’s the hard part: trying to figure out the underlying issue(a). I usually advocate for a change in diet, adding fiber or a laxative and getting these cats up and moving. But these do not usually cure the underlying condition alone. Often a full bloodwork, X-ray and ultra sound are needed to help uncover the cause.
It is also helpful to learn how to palpate your cat so you can tell if the feces is gettin backed up. In some cases I teach people how to give sq fluids at home to help add water and soften the feces to make it easier to pass.