Somebody, I honestly don't remember who, researched this phrase one time and came up with how it originated and what it means in medical terms. The term "end stage" originated in 18th century England.
The patients were lined up on stage and paraded before the medical students,in a large auditorium. Each patient's symptoms were given to the students as they came across the stage and diagnosis were made. Pulmonary patients were placed at the end of the stage or last in line because at that time there was no known treatment. Ergo, "end stage."
Doctors have carried the term forward because, for lack of a better term, they believe they have done all they can do medically!!!
I believe, however, end stage depends on the patient.
If you go to bed, have someone wait on you, give up on life and in general say "I quit" that is endstage. I was diagnosed end stage eight years ago and did all those things myself.