Welcome to SR!
I am so sorry to hear about your ex. I'm sure he must be very frightened.
The only experience I have in this area is with my stepson. He continues to drink, and his liver is on its last legs, so to speak. During his first official hospital detox, he was given a 50-50 shot to make it through with cirrhosis, jaundice, and hepatitis. When the doctor spoke with his father (my late husband), he was told that unless and until he stopped drinking he would not be eligible for a transplant if it came to that.
I can't answer your question as to why he was admitted to the hospital if there is not a liver available. Have you been talking to him? His family? The doctors (if he gave permission for them to talk to you)?
I know you must be frightened, too! I'm so sorry. I know we often don't just stop caring for someone once we break up with them.
The ordinary acts we practice every day at home
are of more importance to the soul than their simplicity might suggest.
~ St. Thomas More