What should I do about the doctor's "maybe"?

My 91 year old father has chronic back pain so we had an MRI. during the MRI, they noticed something on his kidney. His doctor told me during our last visit and asked if we wanted to follow it up with a cat scan or pass. I asked for more info and she said, at his age, what would we do with the information? he is not a surgical candidate. And if its cancer, does it want to know that or would he be better living out his days without the anxiety of the knowledge.. I told her I truly didn't know if Id want to know. She said "think about it; talk to your father, and if you want, then let me know and Ill order the CAT scan"

I did. I think he understood. Sometimes he just stars into space and does her me and sometimes he stares into space and does not hear me. So I asked him if he heard me. He said he did, but that he thought right now we should be worrying more about the heart failure and I agreed. Well, 3 days later the appointment for the cat scan came in the mail and now he doesn't know what's going on. I asked if he remembered us talking about it; he said no, but if something was wrong, he'd want to know so he could "fix it and by more time". I said dad, you know how my stomach sometimes kills me and there is nothing they can do? well, even if they figure out what's in your kidney, they might not have an answer. So now he's worried about whether he should be worried. He worries constantly. He wants me to call the doctor tomorrow and ask her if we should do this and I know that basically means I need to decide whether to get him the cat scan to see whats in the kidney. BTW, there is no blood, no pain. They only saw it from an MRI for his back.

He doesn't have altz, but he has a bad case of PTSD from major battles in WWII. he wakes up sweating and screaming and says "I;m sorry I'm sorry I couldn't save you Davey". I so don't want to know who Davey was.... Our family has never ever talked about things that bother you. Its a family rule.