The main function of colon is to absorb water from poop and push it to the anus so that it may be expelled out of the body. So if colon stops working and does not perform its function, the stool will stay there for a much longer time. During this stay, maximum water will be absorbed from it. As it does not have the capacity to push it forward, so it will get harder. Then the new stool coming from behind will push it further. So, once it is passed out of the body, it will be too hard and will cause a lot of pain. This circle will continue and hardness and pain will increase each day.