Prior to this cat, I rescued a rescue cat from her demented owner, who was one of my patients. He developed an infection inside his leg, and x-rays showed that he had a pin in his leg that had never been removed.
At the very end, just before I had to put him to sleep, he developed a huge tumor on his hip at the infection site, and couldn't get inside the litter box any more. He would stand there with his front legs in, and his back legs out on the carpet...it broke my heart.