Clay litter is especially bad and can certainly cause constipation. It is easy to see on an xray because of its high mineral content.
Do not remove her litter pan because she is used to using it and she knows where it is.
Stop using the litter that you have. Change to a pearl type of litter. Or rabbit pellets. I she eats the latter it won't constipate her.
If she refuses to use the new litter, put a towel in the litter box for her to use. Or the wee pads if she will use that.
But try the new litter first.
Poor Shiloh kitty has a lot of medical problems. Because of her age and her medical condition it is important to keep her as comfortable as possible. Has your vet suggested some warmed subcutaneous fluids to hydrate her? It isn't a long term solution but it might make her feel better and get her eating.
I hope that this has helped you.
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