I am unable to answer you as I don't know his situation or what has already been done. Since he was blocked and overweight, I surmise that he was eating dry food. These are 2 of the most significant negative effects of feeding cats dry food. NO CAT SHOULD EVER EAT DRY FOOD. Unfortunately, at this time, you should speak with the vets at UC Davis to get an answer to your question. Don't be afraid to ask questions. Good luck.