My mom has vascular dementia, but still feels very private about her care for herself. However, she is unable to clean herself well after toileting. So we find "things" on the bathroom floor or find clothes that she has used to wipe herself with. I feel so embarrassed to be having to ask for help with this, but this is the first situation my dad and I haven't been able to work out or talk with her about. She will not let him help her with anything regarding getting dressed, bathing her, or this. So it's falling into my lap to take care of this. Any suggestions would be greatly appreciated ;-)
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.