How do I broach the subject of helping my mom with her toileting?

Adult briefs are always handy to have around (I wouldn't call them diapers). They may cut down on the amount of laundry you have to do but it still doesn't address the issue which is your mom not remembering how to maintain her personal hygiene. She can just as easily use a brief to wipe herself as she's used her underwear and clothes to wipe herself. You'll still have a mess to contend with even with briefs.

Your mom's dignity is very important and her thinking that she's hiding this problem from you is an indication of your mom trying to hang onto her dignity so with her dignity upmost in your mind have a conversation with your mom. Just the two of you, on a level your mom can understand in that moment. Be honest. "Mom, I've noticed urine and feces in your clothes. I'd like to help you stay fresh and clean. Will you let me help you? This can be between just us girls. Dad doesn't have to know."

If she balks don't argue with her but the next time she's in the bathroom knock on the door and ask to come in. Have a fresh pair of panties (or a clean brief) and a new pair of pants with you and say something like, "I thought you might need these." Whisk away the garments around her ankles and tell her that you'll be right outside the door when she's done and you'll help her put her clean pants on.

If you suspect that she's not wiping herself well enough after a BM this would be a good time to address it. After you've gotten her brief/undies and a clean pair of pants and she's standing up tell her she's still a little muddy in back. Don a pair of gloves and use either toilet paper or some wipes to clean her up. You can buy disposable wipes if you prefer that.

All the while this is going on chat with her about nothing. Just keep it light and no big deal. This is a turning point for your mom and it's very difficult for her to be in this position. If you can get her through the first 1 or 2 times I think it will be easier on her and you. Just keep chatting away, taking the focus off of what you're doing, as if you've done this a hundred times before.

From this point going forward it will be easier on your mom to wear elastic waist pants that will go up and down easily.

If your mom continues to refuse to let you in the bathroom when she's in there you may have to override her request that you stay out. She's in your care, you're responsible for keeping her clean and dry and yes, she's entitled to privacy in the bathroom but she's not able to take care of her hygienic needs anymore and needs help in this area. You don't want her to walk around soiled or with an odor. To me, that's worse for her dignity than accepting help in the bathroom. But give her as much control over her own cleanliness as you can up until the point where she needs help staying clean.

This is just one of dozens of little indignities that people with dementia suffer as their diseases progresses and why they need help from loved ones who are caring for them. Your mom will get used to your help in the bathroom in time. It's those first few times that will be the most difficult.

I agree with the comment about the baby wipes, that might help her in the bathroom. It's too bad she won't let her husband help her, you know he's seen her private parts before. You need to approach her gently, go in with her and say Mom, look what I got for you, let me show you how it works. Unless she doesn't even know she's going, and then when she figures out she's wet or dirty she's changing. In that case, you may have to buy adult diapers and hide all her panties. My mom had a stroke and had memory issues, she was also having trouble holding her urine due to being on diuretics. We finally took all her panties away and put the pull ups in their place in the dresser drawer, and she started wearing those. Now there were times we had to go into the bathroom and assist her in changing them, she would wear them soaking wet. The main reason she didn't change was because it was too hard to take her slacks off, put on the clean diaper and then redress. Try the diapers, you can get them in pastel colors, and see if she will wear them.

If she's using clothes and other items to wipe with, then I would suspect that she's just not able to continue doing it for herself. Apparently, she's confused about what to use and how. I think I'd have to ensure that she is accompanied h to the bathroom each time and her needs are taken care of. She will have to get past the embarrassment. Eventually, this happens. There are ways to be very casual about it though. You might just supervise her and see if that helps.

I got my sister a faucet bidet after she broke her back and could not bend or twist to wipe her butt. Easy to hook up and use. Plus make sure she has some baby wipes and paper towels handy for cleanups and a trash can to put them in.