Judith, every drug has POSSIBLE side effects. It's not just because he's a liver patient. Each person has their own body chemistry which reacts differently from another person's. I've taken Ultram and had NO side effects, but it didn't do a thing for my pain, either. I may as well have taken a sugar pill. Conversely, certain drugs I take regularly could flatten another patient while not having that effect on me at all.
I'd mention it to the doctor and see if he can possibly switch him to something else. Then, if the dreams go away, you'll know for sure it was the Ultram.