She completely forgets. Blocks the bowel movement out of her mind completely. Anything else she forgets, I remind her she forgot and she accepts that she forgot and says"oh yes I guess I forgot" but not the bowel movement, if I say to her she had a movement, denies it completely and it would start an argument. Why is that? I don't understand.
The only explanation I ever received and it wasn't so much an explanation as it was a theory. But someone once suggested that when our elderly loved ones were little their mothers thought if they didn't have a bowel movement every day it was somehow unhealthy (in their minds). And that the mom's of our elderly loved ones worked very hard at feeding their kids whatever was necessary to produce a healthy bowel movement every day.
In 20 years in healthcare this is the only explanation I have ever heard as to why the elderly are so obsessed with their bowels and it IS an obsession. I've seen it with my own grandmother. It can be totally irrational.
I've seen it in more women than men. One lady I was providing hospice for would forget that she had a bowel movement and within an hour of having one would insist that she had to go. I'd try to reason with her as she was bed bound and getting her up and down was a major undertaking and I knew she didn't have to go again but I'd get her up and she'd sit and she'd sit and she'd sit and become so frustrated. It finally occurred to me after doing this several times to not empty the commode once she had a BM. She had an indwelling catheter and wore a Depends but she wanted to get up to have a BM which I can understand. So when I got her up to go I didn't empty the commode. Sure enough about 90 minutes later she said she had to have a BM. I tried to dissuade her by explaining to her that she had already gone but she insisted. So I got her up and took her to the commode and showed her her previous BM. I was quite pleased with myself truth be told. I thought I had unlocked the mystery that is bowel obsession. She was confused, didn't remember having a BM, but she believed me and I helped her back to bed. Where I went wrong was emptying the commode at that point. We had to go through it all over again 2 hours later. But live and learn. I learned to keep her BM in the commode throughout my shift with her. I documented it for the next shift and gave a verbal report on why I hadn't cleaned out the commode. And leaving her BM in the commode became standard practice. The lady would still insist on getting up to the commode to have a BM but when she'd see that she already had one she'd accept it and not insist on sitting on the commode for an hour waiting for something that was never going to happen.
Another little trick I learned as BM's can be sticky is to put about 2 inches of water into the commode so when it was emptied the BM would slide right down the toilet.
Again, live and learn.