I am sorry to hear that you are having to deal with this very stressful situation, Leslie. It is important to remember that it is the disease that is causing this, not your aunt deliberately doing it. I have seen success dealing with similar situations using a couple of different approaches. The good news is that it sounds like your aunt has a regular bowel pattern and knows when she needs to defecate, but not where. It may be that your aunt doesn’t remember where the bathroom is or how to get there. Clearly marking the bathroom with a picture or sign, keeping the bathroom door open and a nightlight on at night may help. Have you tried having your aunt sit on the toilet for 10 minutes or so before bedtime? Sometimes just creating that habit will offer a successful solution, similar to toilet training a toddler. Putting a commode at your aunt’s bedside may work because it will be right in front of her if/when she gets up to defecate at night. I would try having her use the commode at bedtime and possibly every few hours during the day as practice, if possible. Even if she doesn’t urinate or defecate, it may cue her about what the commode is used for and make her more comfortable using it. Another approach would be adaptive clothing that prevents your aunt from removing her pajama bottoms and depends. Options include jumpsuit type pjs with a zip up the back, or adding suspender like straps to pajama bottoms, then layering pajama top, bottoms with suspenders, lastly, a back-closing pajama top. Your aunt would still be able to defecate, but into the Depends. You can easily adapt clothing you already have if you sew…or there are websites that offer adaptive clothing, including pajamas. One site I’ve used is Buck & Buck, but there are numerous others as well.
Hope this helps.