Constipation refers to the difficult or infrequent passage of stool. A common definition of constipation is fewer than three spontaneous, complete bowel movements per week.

It is the most common gastrointestinal complaint in the United States, occurring in about 15 to 20 percent of adults. It is also a common pediatric condition. Many cases are related to behavioral issues. However, children also suffer from dietary causes, which include fiber deficiencies, dehydration, and dairy intolerance. Constipation occurs in cystic fibrosis and lead poisoning as well.

Certain medications have constipation as a side effect. These include antihistamines, narcotics, antacids, calcium channel blockers, tricyclic antidepressants, and many other drugs. Drugs are a particularly common cause in the elderly.

Other potential causes include smoking cessation (due to nicotine withdrawal), Parkinson's disease, hemorrhoids, and hormonal disturbances (e.g., hypothyroidism).

Symptoms

• Hard, dry stool, which is difficult to pass or leaves the sensation of incomplete passage
• Infrequent bowel movements
• Bloating and abdominal discomfort. These symptoms are more common in irritable bowel syndrome (IBS) than constipation from other causes. IBS can be differentiated from simple constipation by the presence of other digestive symptoms.
• In severe, long-standing cases, low-back pain, rectal bleeding, or hemorrhoids may occur.

Risk Factors

The highest reported prevalence occurs in persons over age 60, followed by children under age 10. The association with age is largely attributable to other factors, such as medication and diet.

For reasons that are unclear, Caucasians report constipation less frequently than do other racial groups, and women are affected approximately twice as often as men. The condition is more common in poorer individuals. Additional possible risk factors include family history, pelvic floor dysfunction, pelvic and abdominal surgery, and childbirth.

Constipation: Diagnosis and Treatment

Diagnosis

• History and physical examination, including rectal exam, can establish the diagnosis.
• A detailed bowel diary, submitted by a patient or parent, may be helpful. Many people misjudge normal bowel function as abnormal.
• Blood testing is necessary if hypothyroidism, anorexia, hypercalcemia, or diabetes is suspected. These conditions may also apply in children, as may celiac disease, lead poisoning, cystic fibrosis, and urinary tract infection.
• X-ray of the abdomen can detect certain disorders and is also useful in monitoring hospitalized patients.
• Rarely, colonoscopy may be necessary to rule out obstruction or colon cancer.

Treatment

• The first step is to identify and treat a possible underlying cause, such as discontinuing or changing causative medications.
• Often, the most effective treatment is to increase fiber and fluid intake, and consume foods that reduce transit time of the stool through the intestine, such as fruit juices with sorbitol.
• Biofeedback and behavioral changes may be helpful in some cases, especially in children. Biofeedback is a psychological technique in which patients are trained to recognize and respond to signals from their own bodies.
• Severe constipation may require a multidimensional approach that includes manual disimpaction.
• Drug therapy may include:
  
  • Bulk-forming agents (e.g., oral fiber supplements, such as psyllium)
  • Hyperosmolar agents (e.g., lactulose, sorbitol, and glycerin)
  • Emollients (e.g., docusate or mineral oil), which soften stools, but are less effective than other drugs.
  • Stimulants (e.g., senna, bisacodyl, and castor oil), which increase movement of the intestines. These are not suitable for long-term use.
  • Prokinetic agents (misoprostol, colchicine, and tegaserod)

Many of these drugs can be used in children, but doses must be adjusted accordingly. Enemas and stimulant laxatives should not be used in infants.

Laxatives are not generally recommended, because they prevent the bowel from recovering normal function and often need to be continued. Although they are generally well tolerated, laxatives may cause abdominal distention, nausea, anorexia, cramps, gas, and (rarely) malabsorption or dangerous chemical imbalances.

• Biofeedback training to exercise the anal musculature and sphincter may be useful in some patients, especially those with pelvic floor muscle dysfunction.
• Rarely, surgery may be an option for patients with severe symptoms.

Physical activity has been shown to be effective to improve symptoms. Individuals who report daily physical activity have roughly half the risk for constipation, compared with those who are least active. When higher levels of both activity and fiber intake are paired, the risk for constipation drops roughly 70 percent, compared with individuals who are least active and eat the least fiber.

Constipation: Nutritional Considerations

• Increasing intake of high-fiber foods: The most common cause of constipation is a diet low in fiber. Fiber is found only in plant-derived foods, such as beans, vegetables, fruits, and whole grains. In contrast, animal-derived foods and heavily processed food products do not contain fiber.
  
  Americans eat an average of 5 to 14 grams of fiber daily, far less than individuals residing in less-developed countries. In persons eating more traditional, higher-fiber diets, constipation is rare. Increasing dietary fiber intake has been shown to improve constipation and significantly reduce the need for laxatives, especially in children, the elderly, and postsurgery patients.
  
  Although high-fiber foods should generally be the first choice, some patients may benefit from fiber supplements. Evidence indicates that fiber supplements permit discontinuation of laxatives in about 70 percent of constipated patients. Several types of fiber supplements have been shown to be effective for constipation relief, including psyllium (Metamucil), methylcellulose (Citrucel), and Japanese konjac root (glucomannan).

• Increasing fluid intake: Poor fluid intake is commonly associated with constipation, especially in children. In one study, a combination of 25 grams of fiber and 1.5 to 2.0 liters of fluid daily was more effective treatment for constipation than fiber intake alone.

• Avoiding cow's milk: Many children with chronic constipation have cow's milk allergy. One study showed that up to two-thirds of constipated children with cow's milk sensitivity may have improved symptoms when they remove milk from their diets. Further, a controlled clinical trial found that constipation returned within five to 10 days after reintroduction of cow's milk.
  
  It is important to realize that cow's milk is not the only source of calcium. If poor calcium intake is a concern, calcium-fortified soymilk, rice milk, or juices may be substituted for cow's milk.