Constipation is a common disorder that is often defined differently by patients and physicians. Clinically, constipation occurs when bowel move- ments are difficult or painful. The "normality" of bowel movements, in terms of frequency, varies among individuals; frequency that is thought by one person to be constipation may be reported by another to be usual and thus normal. Often the perceived "need" to have a bowel movement leads to self-treatment...