This article has confirmation from the GUR, Ukrainian military intelligence, that Kadyrov is critically ill. There are no exact details on what he has other than that it's related to a chronic health condition, potentially kidney failure given his facial swelling. It's also long been reported that he's an addict.

I also call attention to the fact that Kadyrov allegedly had his personal physician executed in suspicion that the latter was poisoning him. It would truly be poetic justice if denying himself that medical treatment in a fit of paranoia precipitated this (hopefully terminal) episode.