Constipation: physiopathology and classification

Constipation is commonly defined on the basis of the number of bowel movements in a week (greater than 3 week) or on the stool weight (less than 35 g/day) and on their consistency and expulsion capacity. A pathophysiological classification of constipation subdivides the patients into 2 groups. The first includes those patients in which a propulsion defect is prevalent (inertia coli) and the second one comprehends those in which a predominant expulsion defect is found. This second group consists of patients with myogenic, neurogenic or mechanical disorders. Moreover, we can consider in this group those patients with irritable bowel syndrome (IBS) who show a reduction of rectal compliance and those who produce "inappropriate stools". Finally, in this group we can find those patients having the so-called faecal impaction, that is an abnormality of either sensitivity or stimulus to defecate frequently observed in the elderly and in children.