There is no one reason that pediatric constipation may occur, but it is commonly caused by developmental changes or changes in routine. For example, children who are starting school may hold in bowel movements, which can cause constipation. Children who are toilet training may resist going to the bathroom because they don’t want to stop playing. Sometimes a medication, such as a strong pain medication, can cause constipation in children. Underlying medical conditions, such as abnormal nerves in the colon and celiac disease, can also cause constipation. But fewer than 5% of children who experience constipation have an underlying medical disorder.