Colonic inertia disorders in pediatrics include a large number of conditions with diverse etiologies and different pathophysiologic mechanisms (Table 1). Of all of these, we selected those that are most common, have more social impact, and have more clinical importance for surgeons. Idiopathic Constipation Definition and Terminology Idiopathic constipation is the incapacity or difficulty to pass stool regularly and efficiently. The cause of this condition is unknown. We intentionally use the term idiopathic because we believe that, even when there are many proposed explanations for the cause of this condition, none of these explanations have scientific basis. In agreement with Benjamin Disraeli, we believe that "to be conscious that you are ignorant is a great step to knowledge." 1 Incidence, Relevance, and Social Impact Idiopathic constipation is by far the most common defecation disorder and the most common colonic motility disorder in children. This condition affects an enormous pediatric population and represents a common cause for surgical consultation. 2-4 It is relevant not only because it affects millions of Americans but also because it is extremely incapacitating in its most serious forms. In fact, it produces a form of fecal incontinence that is known as encopresis or overflow pseudo-incontinence. The most serious type of constipation cannot be differentiated from a very serious motility disorder called intestinal pseudo-obstruction that carries a significant mortality rate. 5,6 Causes and Pathogenesis Although the cause of idiopathic constipation is unknown, the literature presents many potential causes for the disease. Most of the proposed explanations have no solid scientific basis, however. There are many