A disease affecting the colon, Hirschsprung disease (also called Hirschsprung's disease) often results in severe constipation. In fact, some children with the disease can't have bowel movements at all. It usually occurs in children before birth; however, the exact cause is unclear.
Hirschsprung disease is a serious disorder that needs to be treated right away. Potential complications of leaving it untreated include infection, bursting of the colon, and even death. Treatment generally involves options such as pull-through surgery or, sometimes, an ostomy. Most children with this disease lead normal lives after treatment.
(For more information, including a detailed description of how the intestines work, click Hirschsprung's Disease.)