I agree with KD.....although I would use skinless, boneless boiled chicken breast instead of the ground beef. Beef is more of a complex protein than chicken and thus would be a bit harder on the digestive tract. Our vet always recommends boiled chicken breast, nothing added to flavor it, plus white rice. Once you've boiled the chicken breast, you could use the water(with the chicken flavoring in it) to try and entice him to drink it. If he does well with that then move on to the chicken/rice. When one of our dogs had cancer I would puree the chicken/rice mixture and feed it to her through a syringe. She too wouldn't eat anything but this seemed to wake up her taste buds for some reason. Good luck with your dog.
I hope he makes a full recovery!!!!