Everything listed in this website is perfect. The tricky part is fully understanding what interoception means. Without experiencing, it is quite hard for some to imagine. Still I would encourage parents to try and visualise how it can be very confusing if you cannot differentiate the feelings in bowel or stool or pain in the body. Imagine what would you do if the muscles of these body parts are floating in space and the different pains exist elsewhere other than where it should be. Or that you thought u were going to pee but end up pooping instead.
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​For girls, there is also such a thing as, the child has not peed finish, leaving droplets dripping out slowly after going toilet. The key thing here is to wait another 2mins or so until it is completely finished. This is an example of the challenge of not being able to feel that. Some are so afraid of the feeling of pain due to constipation that they will keep it inside hoping the pain will go away. The pain is real, their tears is real. The other challenge would be, how to control the anus, when such happens. Because there is also the challenge of pushing, while holding the anus shut tight. Which causes lighting type of pain. The lack of control, breathing techniques, requires parents to teach in precision, and even learning how to control pelvic muscles as well as anus muscles. 
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​Then read the article again and try to devise a plan. To teach such a brain. I believe this plan will be most effective :)
Remember, Individualise, Individualise, Individualise!

Take a look and get inspired to make your own! The more you individualise, the higher the success rate would be!