 Hi, my name is Dr. Radhakrishnan. I'm a pediatric surgeon and a pediatric urologist and I work at the Manipal Hospital in Bangalore. By far the commonest cause of childhood constipation is habitual and really can be seen at any age in a child, but most commonly appears as the child's diet is changing at about a year and a half to two years of age. What happens is this at some point a child has a hard painful stool. It could be that they are dehydrated on a hot day, that they are on some medication that's made the stool hard or some other cause. Once they pass a hard painful stool, their brain starts to then tell them that they must not go because it will hurt and they stop going. The next time they go it's again another hard painful stool and this becomes a vicious cycle leading to constipation. Thank you for watching.