37 Constipation
Key Points• Constipation has a variety of meanings to patients. Ask about pain, stool frequency, stool hardness, and difficulty with passage.
• Dangerous conditions such as early bowel obstruction can mimic functional constipation, especially in the elderly. Red flags include severe pain, vomiting, fever, gastrointestinal bleeding, acute onset without an obvious cause (e.g., opiate use), peritoneal signs, and significant systemic symptoms.
• In most patients, constipation has a functional, nonemergency cause that is often related to medications or lifestyle habits such as dietary fiber intake, fluid intake, and toileting.
• The treatment goal for uncomplicated constipation consists of initial cleansing, a maintenance plan, and preventive lifestyle changes.
• A wide range of underlying conditions, such as malignancy and systemic disorders, can cause constipation. Primary care follow-up is warranted.
Perspective
Epidemiology
Constipation is common at all ages, with the reported prevalence ranging from 2% to 27%,1 depending on the definition used. Prevalence is higher in women than in men (approximately 2 : 1), perhaps related to an increased prevalence of pelvic floor dyssynergy in women.2 Prevalence is higher in the elderly: in those older than 84 years, self-reported rates are 25.7% in men and 34.1% in women,3 and up to 74% of elderly nursing home residents are taking laxatives daily.2 The condition is much less common in populations with non-Western diets containing more bulk. Although many people do not seek medical attention for their constipation, this condition is estimated to result in almost $7 billion in medical costs in the United States each year.3
Pathophysiology
Constipation is often multifactorial, with disordered movement of stool through the colon and anorectum. Oral intake, hydration, and general mobility affect colonic function. Numerous anatomic and structural entities, gastrointestinal (GI) disorders, medications, and systemic disorders may secondarily lead to constipation (Boxes 37.1 to 37.4) by altering intraluminal contents, fluid balance, intestinal contractions, or neuromuscular coordination. However, the majority of patients have primary chronic functional constipation that falls into one or more of three categories. Many actually have normal intestinal transit time; their constipation is perceptual and related to habits. Others have slow transit times because of overall colonic slowing (pancolonic inertia) or sigmoid spasm (left colonic hypermotility with uncoordinated segmental contractions and poor propulsion). An important but underrecognized group has pelvic floor dyssynergy (obstructive defecation), an acquired behavioral condition that begins with chronically ignoring the urge to defecate. Disordered defecatory function of the pelvic floor muscles and sphincters eventually produces difficulty expelling stool, even if soft. Hormonal contributions are unclear, but constipation is common in pregnancy4 and before menstruation. Contrary to past thinking, chronic laxative abuse does not cause chronic constipation.5 High rates in the elderly are not due to aging itself but to concomitant conditions or medications.6
Box 37.2 Systemic Causes of Constipation
