Chapter 131

Constipation

Courtney L. Betts

Definition and Epidemiology

Constipation, one of the most common gastrointestinal complaints in the United States, results in almost 8 million primary care visits each year, with an estimated 230 million dollars spent annually in medical costs and more than 820 million dollars spent on laxatives.¹^,² This chronic disorder disproportionally affects women, children, older adults, people of low socioeconomic status, obese patients, and non-white individuals.³ Whereas older adults are more affected and may be predisposed to constipation, there are no significant studies showing that the colonic musculature atrophies with age.⁴ Rather, the increased incidence in older adults is most likely secondary to diminished vitality, decreased fluid intake, diets high in fat and protein and low in fiber, decreased activity, and the consequences of many illnesses and medications (Box 131-1).⁴ Although it is not usually considered life-threatening, constipation can be disconcerting and disabling and can cause a decrease in quality of life, especially for older women.⁵ It can also be associated with hemorrhoids, anal fissures, rectal prolapse, impaction, and ileus.⁶

Box 131-1

Medications Associated with Constipation

• 5-HT₃ receptor antagonists (Ondansetron)

• Antacids

• Anticholinergics

• Antidepressants (selective serotonin reuptake inhibitors and tricyclic antidepressants)

• Antihistamines

• Anticonvulsants

• Calcium channel blockers

• Clonidine (Catapres)

• Calcium supplements

• Diuretics

• Iron supplements

• Levodopa (Larodopa)

• Narcotics

• Nonsteroidal anti-inflammatory drugs

• Psychotropics

• Sympathomimetics

Data from Bharucha AE, Pemberton JH, Locke GR: American Gastroenterological Association technical review on constipation. Gastroenterology 144:218-238, 2013.

Constipation is usually defined by practitioners as a decrease in the frequency of bowel movements to fewer than three per week.⁷ However, for the Rome III criteria for constipation to be fulfilled, two or more of the following must have been present for at least 3 months with onset 6 months before diagnosis: fewer than three bowel movements per week, the passage of hard or lumpy stools, a sensation of straining, a feeling of incomplete evacuation or anorectal obstruction, and use of manual maneuvers to aid defecation in more than 25% of defecations.⁸ In addition, soft, easily passed stools are not present without the use of medication such as laxatives, and the patient does not meet criteria for irritable bowel syndrome.⁸ A true clinical diagnosis is the finding of a large amount of feces in the rectal ampulla on digital examination or excessive feces in the colon, rectum, or both on the abdominal radiograph.

Pathophysiology

The primary function of the large intestine is to store and to concentrate fecal material before defecation. If the fecal contents remain in the large intestine for long periods, almost all water is absorbed, resulting in hard stools. Normal colonic motility depends on the integrity of the central nervous system, autonomic nervous system, gut wall innervation and receptors, circular smooth muscle, gastrointestinal neurotransmitters, and hormones. Healthy adults have normal gut transit time; total gut transit time is prolonged in patients with constipation.

Causes of constipation can be classified as either primary or secondary. Primary causes are disordered colonic transit (normal or slow transit) and defecatory disorders (a failure to adequately empty the rectal contents).² Secondary causes are related to medical and psychogenic conditions, medications, structural abnormalities, and lifestyle.¹^,² These include ignoring the urge to defecate; inadequate fiber or fluid intake; medications; pregnancy; Hirschsprung disease; hypothyroidism; hypoparathyroidism; diabetes; hypokalemia; hypercalcemia; motility disorders; psychological disturbances; and neurologic disorders, such as Parkinson disease, multiple sclerosis, and disorders of the peripheral or central nervous system.¹^,²^,⁹ Fistulas, hemorrhoids, rectoceles, abscesses, neoplasms, and other functional abnormalities are also associated with constipation, but the cause can be idiopathic or even related to irritable bowel syndrome. Parasitic infections, such as with Ascaris lumbricoides (an intestinal roundworm), have been identified with intestinal obstruction and should be considered in patients who travel to or live in endemic areas.¹⁰

Clinical Presentation and Physical Examination

Constipation is a subjective complaint and varies from one individual to another. Patients may have daily bowel movements but still feel constipated.⁷ Patients may complain of constipation and describe a feeling of nausea, bloating, straining, and cramping and difficulty passing stools. The patient history should include when the change in bowel pattern occurred; the number of stools per day and week; the last bowel movement; the need to strain during defecation; the sensation of incomplete evacuation; the need to self-disimpact; and any episodes of fecal incontinence, diarrhea, abdominal pain, or blood or pain with defecation.⁷^,¹¹ Patients who indicate that their main concerns are incomplete evacuation, feeling of obstruction, and manual disimpaction may have a defecatory disorder.⁹ Possible systemic, neurologic, or other related symptoms should be elicited in addition to a past history of associated illnesses, a 24-hour dietary and fluid review, and a complete medication review (including laxative and over-the-counter medication use). Alarm symptoms and factors include sudden change in bowel habits, weight loss of 10 pounds or more, blood in the stool, anemia, family history of colon cancer or inflammatory bowel disease, constipation resistant to treatment, and age older than 50.¹^,¹¹

Although it is not uncommon to have normal findings, the physical examination is performed to exclude or to verify the symptoms of constipation. Orthostatic hypotension or tachycardia implies dehydration; weight loss suggests anorexia or carcinoma. The oral examination may suggest poor dentition, ill-fitting dentures, lesions, or dehydration. Abdominal scars indicate a surgical history. Peristalsis and bowel sounds may be increased or decreased, suggesting a threatened obstruction or ileus. There may be increased dullness over areas of stool, and masses may be palpated. Rebound tenderness suggests a peritoneal inflammation. A gynecologic examination may demonstrate a rectocele. A digital rectal examination should determine anal abnormalities, sphincter tone and function, pain, lesions, rectal prolapse, impaction, hemorrhoids, or fissures. The neurologic examination may elicit autonomic dysfunction or neuropathy. Perineal descent is assessed by having the patient bear down while lying in the left lateral position (normal perineal descent while straining is 1 to 4 cm [ to inches]).