My grandfather has been battling Leukemia for several years now.  He was very sick last year with pneumonia, and that is when we discovered it was worse than we thought.  Once he was able to recover from the infection, he started chemo therapy.

A few weeks ago, he was having abdominal pain and we learned that he had a gallstone.  He underwent surgery and it was removed.  He appeared to recover fine from the surgery immediately after. 

However, a few days after the surgery, everything started to change and he is now in a state of constant confusion and fatigue.  He cannot remember his address or common details of his life.  He still seems to recognize people okay, though it does take him a minute to place them, as though he is really thinking about it.  Also, he is now having difficulty walking.  He has fallen a couple times and injured himself, which has led him back to the hospital.

It is almost like a dementia or even Alzheimer's, but it just came on so rapidly and has been going on for about a month now.  It also seems to be getting worse, not better.

My grandmother is not getting any answers from the doctors and our entire family is wondering what in the world is going on here. 

Is this a final stage of leukemia?  Or is this perhaps related to the surgery he underwent to have the gallstone removed?  I feel so ignorant about everything pertaining to this disease, so any insight this community could offer would be greatly appreciated.

We're all just wondering if this is the end... If we need to prepare ourselves.  Or is this something entirely unrelated?