Tiddles, a male grey and white cat was found at the gates of the RSPCA’s Blackberry Farm Animal Centre in Aylesbury on Thursday.
He had a leg injuries so severe that one of his back limbs is going to have to be amputated.
But the good-looking moggy is now making progress on pain relief medication.
Julie Allen, manager at Blackberry Farm, said: “The poor cat was left in an insecure cat litter tray and had obviously been there for some time, possibly overnight, because the dry food that he had been left with was sodden and the litter he was sitting on was very wet. “
She added: “One of his femurs was absolutely smashed beyond repair and unfortunately his leg will have to be amputated. I dread to think how much pain this poor cat would have been in.
“We have made him comfortable and given him pain relief. He is also getting a lot of love from members of staff.
“We are just at a loss as to why someone could be so cruel. First to not take this lovely cat to a vet and secondly to callously dump him in such a dreadful condition.”