Obsession with bowels

My mother is 89 years old and suffers from depression and dementia. Recently she was hospitalized for an artery blockage in her leg, and then went to a nursing home for therapy. Ever since she was in the hospital she has had an obsession with going to the bathroom. She thinks she has to have a bowel movement every 10 or 15 minutes, but nothing happens. The nurses say that she does have a regular bowel movement every day. Do you think this obsession is caused by anxiety, depression or dementia? What can we do?

I guess anxiety. Let her lie on her bed and feel the movements until they disappear. Ask her about her feelings at the same time.