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INTRODUCTION AND EPIDEMIOLOGY
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Constipation is an extraordinarily common cause of patient morbidity.1-4 The incidence of constipation increases with age, with overall prevalence rates in North America from 12% to 19%.5 Constipation affects as many as 80% of critically ill patients and is directly associated with patient mortality in this population.6
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Physicians and patients define constipation differently. Physicians have traditionally defined constipation as fewer than three bowel movements per week. Patients commonly define constipation in terms of symptoms such as abdominal discomfort, bloating, straining during bowel movements, or the sensation of incomplete evacuation. Constipation should not be defined simply by stool frequency alone, because doing so can lead to underdiagnosis for a significant number of patients who suffer from the condition.7 The Rome criteria for the definition of constipation consist of two or more of the following signs or symptoms: (1) straining at defecation at least 25% of the time, (2) hard stools at least 25% of the time, (3) incomplete evacuation at least 25% of the time, (4) fewer than three bowel movements per week, and (5) rarely having loose stools without the use of laxatives and having symptoms for at least 3 months in the preceding 6 months for chronic constipation.8
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Constipation is a complicated condition with multiple, often overlapping causes (Table 74-1). Gut motility is affected by diet, activity level, anatomic lesions, neurologic conditions, medications, toxins, hormone levels, rheumatologic conditions, microorganisms, and psychiatric conditions. Constipation is best thought of as either acute or chronic, as doing so helps formulate a differential diagnosis (Table 74-1). Acute constipation should primarily prompt evaluation for intestinal obstruction, and history and physical examination can identify other causes. Chronic constipation can be caused by many of the same conditions that cause acute constipation (Table 74-1).
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The differential diagnosis of constipation is broad, so obtain a thorough history. Determine when the symptoms started and if there are any temporally related clues that can help narrow the differential diagnosis. Was a new medication or dietary supplement added at that time? Was there a decrease in fiber ...