Constipation refers to the difficult or infrequent passage of stool. A common definition of constipation is fewer than 3 spontaneous, complete bowel movements per week. However, the need to strain, the consistency of stool, and the sensation of incomplete evacuation or blockage have also been included in other definitions.
Constipation is also a common complaint in children. Many cases are related to behavioral issues, such as voluntary stool withholding due to stress, social or environmental changes, or pain. However, the condition can result from dietary causes, including fiber deficiency, dehydration, and dairy intolerance. Constipation also results from numerous disorders, such as cystic fibrosis, hypothyroidism, diabetes mellitus, and lead poisoning.
The etiology of constipation is typically multifactorial. Constipation can be considered either primary (due to some type of colorectal dysfunction) or secondary (related to other factors). Primary colorectal dysfunction can be broken into subtypes: normal-transit (functional) constipation, slow-transit constipation, dyssynergic defecation (disorganized contraction or relaxation of the pelvic floor, resulting in inadequate rectal propulsive forces or increased resistance to evacuation), and constipation-predominant irritable bowel syndrome (IBS). Normal-transit constipation is the most common type of constipation seen by clinicians. This diagnosis is characterized by patient report of hard or infrequent stools, but testing does not reveal decreased transit, and stool frequency is within normal range.
Common identifiable secondary causes in adults include:
- Medications (e.g., narcotics, antacids, calcium channel blockers, tricyclic antidepressants, and many other drugs), particularly in older adults
- Smoking cessation (constipation is a temporary result of nicotine withdrawal)
- Anatomical obstructions (e.g., tumor, stricture, third-trimester pregnancy, anal canal disease)
- Anal pathology (hemorrhoids, abscesses, fistulae, and fissures), which can decrease the desire to defecate due to pain
- Neurologic diseases (Parkinson’s disease, multiple sclerosis)
- Metabolic disease (diabetes mellitus, hypothyroidism)
Symptoms and signs of constipation include:
Complaints of hard, dry stool that is difficult to pass or leaves the sensation of incomplete evacuation.
Infrequent bowel movements.
Abdominal pain with or without palpable fullness in the left lower abdomen.
Bloating and vague abdominal discomfort. These symptoms are more common in IBS than in simple constipation. IBS can be differentiated from simple constipation by the presence of discomfort or pain that occurs prior to defecation and that is relieved with defecation (see Irritable Bowel Syndrome chapter).
Lower back pain. Pain is uncommon in idiopathic chronic constipation.
Rectal bleeding (e.g., fissures, ulcerations/erosions).
Uncommon symptoms include headaches, due to straining, and vomiting, in cases of complete obstruction.
The highest reported prevalence of constipation occurs in persons over 65 years of age, followed by children under age 10. Institutionalized elderly persons appear to be at higher risk for constipation than those living in the community. The association with age is largely attributable to other factors, such as medication, diet, and exercise. For unclear reasons, in North America, whites 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 individuals with relatively low income and less education.
Additional possible risk factors include:
Careful history and rectal examination (routinely performed in adults but only as needed in children) can establish the diagnosis, and physical examination may help identify causes of secondary constipation. The Rome IV criteria are used to make a diagnosis of primary constipation:
- Must include at least 2 of the following during the previous 3 months, with symptom onset at least 6 months before diagnosis:
- Straining during more than 25% of defecations
- Lumpy or hard stools (Bristol Stool Form Scale type 1 or 2) in more than 25% of defecations
- Sensation of incomplete evacuation in more than 25% of defecations
- Sensation of anorectal obstruction or blockage in more than 25% of defecations
- Manual maneuvers needed to facilitate more than 25% of defecations
- Fewer than 3 spontaneous bowel movements per week
- Loose stools are rarely present without laxatives.
- Criteria for irritable bowel syndrome are not met.
Identification of drug side effects in adults, including those from the use of over-the-counter products such as antacids and iron supplements, does not negate the need for further evaluation. Drugs may make evident a problem that had not previously been apparent.
A detailed bowel habits diary, submitted by a patient or parent, may be helpful. Many people misjudge normal bowel function as abnormal.
Laboratory evaluation, imaging, and endoscopy should be reserved for select individuals. There is lack of evidence to support a routine workup in patients unless alarm features are present. Such features include the following: hematochezia, weight loss of ≥ 10 pounds, a family history of colon cancer or inflammatory bowel disease, anemia, positive fecal occult blood tests, or acute onset of constipation in the elderly. Other situations in which laboratory evaluation is typically indicated include those where hypothyroidism, anorexia, hypercalcemia, diabetes, celiac disease, lead poisoning, cystic fibrosis, or urinary tract infection are suspected. These conditions may also apply in children.
Plain film imaging of the abdomen can detect the presence of stool and can suggest megacolon or megarectum. Plain films are helpful when no alarm symptoms are present and when a patient has not responded to conservative therapy. Plain films can also be used to monitor progress in a hospitalized patient. In cases of intra-abdominal bowel distention, plain films often cannot distinguish ileus from mechanical obstruction. If Hirschsprung’s disease is suspected, a barium radiograph should be obtained.
A CT scan may be utilized in certain circumstances, such as in undifferentiated severe abdominal or back pain.
Endoscopy is necessary when alarm symptoms are present, or in any patient over age 50 who is not up to date with colon cancer screening, in those with a strong family history of colon cancer, and in those for whom surgery is being considered for treatment of severe constipation. Additionally, patients may be candidates for endoscopy if they present without alarm symptoms or other symptoms of organic disease and have failed a trial of conservative therapy.
If history, physical examination, and imaging studies are normal, colonic transit studies (radiopaque marker studies) or motility studies (colonic or anorectal manometry) can help identify less common causes of constipation.
Treatment of any identified cause should be attempted before medications are considered. For functional constipation, conservative therapy is preferred, which includes patient education and dietary changes. When disimpaction is necessary, bulk-forming laxatives and/or non-bulk-forming laxatives or enemas can be used. The combination of fiber and fluid intake influences stool output in a dose-response relationship (see Nutritional Considerations below). Physical activity may also be beneficial.
Many of the drugs below can be used in children, but doses must be adjusted accordingly. Many of these remedies are available in oral form and as rectal suppositories and enemas. For toilet-trained children, the typical duration of medical treatment for functional constipation is at least 2 months. It should then be gradually discontinued only after complete resolution of constipation symptoms for a month. For children in the developmental stages of toilet training, the treatments are usually stopped only when toilet training has successfully been achieved.
Simple therapies, including supplemental fruit juices with sorbitol (for infants already eating solid foods) and those therapies mentioned above, should be tried first. Glycerin suppositories or rectal stimulation with a lubricated thermometer may occasionally be used if absolutely required. Enemas and stimulant laxatives should not be used in infants.
Laxatives should be considered only when an adequate trial of conservative therapy has failed or in complicated cases. Although they are generally well tolerated, laxatives may cause abdominal distention, nausea, anorexia, cramps, gas, and (rarely) diarrhea severe enough to produce malabsorption or dangerous electrolyte imbalances, which may worsen with continual use. Clinicians should be cautious of these implications when prescribing laxatives.
Bulk-forming agents (e.g., oral fiber supplements such as psyllium, methylcellulose, and polycarbophil) hold water in the intestinal contents, increasing and softening fecal bulk. However, they can also worsen symptoms of constipation, and patients should be warned of this possibility prior to initiating supplements.
Emollients, such as docusate and mineral oil, soften stools but are not always very effective. Mineral oil should be avoided in infants and those with significant gastroesophageal reflex as aspiration can cause severe lipoid pneumonia.
Hyperosmolar agents, which cannot be absorbed, produce diarrhea through an osmotic fluid shift.
- Magnesium salts are effective for rapid emptying and intended for one-time use. Hypermagnesemia can occur with frequent use.
- Lactulose works more slowly than salts and may be used for long-term treatment when diet therapy is not possible or ineffective. It may cause gas.
- Sorbitol is less expensive than lactulose and functions similarly.
- Glycerin is available as a suppository.
- Polyethylene glycol formulations (GoLYTELY or MiraLax) do not contain electrolytes. These products are typically well tolerated and efficacious. They can be used in children older than 1 year and are recommended as the first line of maintenance treatment and for children presenting with fecal impaction.
Stimulants or contact irritants increase peristalsis. They include senna, bisacodyl, and castor oil. With long-term use, stimulant laxatives can lead to electrolyte imbalances and, in rare cases, to dependency.
Additional Treatments for Adult Patients
Misoprostol has shown to be beneficial but is contraindicated in women of childbearing age.
Colchicine can improve symptoms. It is contraindicated in those with renal disease.
Lubiprostone is a chloride channel agonist that increases intestinal fluid secretion. Side effects include nausea and diarrhea. Its role in treatment has yet to be determined.
Linaclotide is a minimally absorbed peptide that stimulates intestinal fluid secretion and transit. It has been approved by the US Food and Drug Administration for the treatment of chronic idiopathic constipation. The long-term risks have not been well studied.
Some evidence suggests that a botulism toxin injection (into puborectalis muscle) may benefit those with pelvic floor or defecation dysfunction. Repeated injections seem to be necessary to maintain benefits.
If slow transit is not present, the patient may have pelvic floor dysfunction (dyssynergic defecation), which may respond to pelvic floor exercises or biofeedback. The rationale for biofeedback treatment is based on the observation that inappropriate (paradoxical) contraction or a failed relaxation of the puborectal muscle and of the external anal sphincter often occurs during attempts to defecate and is considered a form of maladaptive learning. Although additional long-term studies are required, the available evidence indicates that biofeedback training provides a significantly higher probability of successful outcome in treatment of functional constipation and functional fecal incontinence than does standard medical care. Biofeedback and behavioral changes may also be helpful in children.
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%, compared with that of individuals who are least active and eat the least fiber.
Severe constipation may require a multidimensional approach that includes manual disimpaction or possibly even surgery. Surgery typically includes subtotal colectomy with ileorectal anastomosis and has strict qualification requirements.
Constipation is common in developed countries. According to most estimates, 20% of North Americans are affected, which is similar to the percentage of people affected in other Westernized cultures. The most common association is with a low-fiber diet. Fiber is found only in plant-derived foods such as beans, vegetables, fruits, and whole grains and is absent in meat, dairy products, and eggs. The average daily fiber intake for Americans age 2 years and older is 16 g; established recommendations range from 19-38 g per day. In countries where traditional diets are higher in fiber, constipation is less common. Then, when a lower-fiber, Western diet is adopted, constipation prevalence increases.
The following considerations are most important in preventing or alleviating constipation:
Increasing high-fiber foods. A lower intake of dietary fiber differentiates children with chronic constipation from those with regular bowel habits. Increasing dietary fiber improves constipation and significantly reduces the need for laxatives in children, young adults, seniors, and postsurgery patients.
Although high-fiber foods should generally be the first choice, there may be a role for fiber supplements in some individuals (e.g., edentulous patients or those with dysphagia). Evidence indicates that fiber supplements permit discontinuation of laxatives in about 60% of constipated patients. Several types of fiber supplements are useful for constipation relief, including psyllium (Metamucil), methylcellulose (Citrucel), and Japanese konjac root (glucomannan).
Increasing fluid intake. A hypohydration or dehydrated state contributes to constipation. Inadequate fluid intake is a reason for constipated children. A combination of 25 g of fiber and 1.5-2.0 L of fluid daily was more effective for constipation relief than fiber intake alone in patients with functional chronic constipation.
Avoiding cow’s milk. Many children with chronic constipation are allergic to cow’s milk, manifesting IgE antibodies to cow’s milk antigens. Cow’s milk consumption is also significantly higher in infants and children with constipation and anal fissure than in those without these disorders. In roughly half of constipated, cow’s milk-allergic children and adolescents who have had a colonoscopy, nodular lymphoid hyperplasia was found, compared with 20% of controls. In one-third of all cow’s milk-allergic individuals, there are a significantly higher number of intraepithelial T cells, indicating an enhancement of local immune responses against food antigens. Immune activation is known to affect gastric motility, possibly indicating a role for an immune response to food antigens in constipation. Roughly one-third to two-thirds of constipated children with cow’s milk sensitivity improve on milk-free diets. In a small crossover study, 100% of participants had full resolution of chronic functional constipation when soy milk replaced cow’s milk. Another controlled clinical trial found that constipation returned within 5-10 days of the reintroduction of cow’s milk.
There is no nutritional requirement for cow’s milk, and relief of constipation for some individuals is one of many reasons to avoid it. When calcium adequacy is in question, calcium-fortified nondairy beverages such as soy milk, rice milk, or almond milk can be used in place of cow’s milk.
What to Tell the Family
Constipation is a common disorder that is usually preventable with a diet high in minimally processed, high-fiber foods; consumption of ≥ 1.5-2.0 liters of fluid per day; and regular exercise. Health practitioners can provide helpful information about dietary approaches to prevention and treatment.
Most patients and their families are not fully aware of the best sources of dietary fiber (beans and other legumes, vegetables, fruits, and whole grains) or of the absence of fiber in animal-derived or heavily processed food products. They may also have been inappropriately influenced by advertisements for over-the-counter treatments or specific foods, such as breakfast cereals and snack bars.
Children with cow’s milk sensitivity may respond to the removal of dairy products from their diet. Parents of children with behavioral aspects that contribute to constipation, such as stool withholding in response to anxiety, family stress, or painful defecation, should be encouraged to discuss a behavior modification program with the child’s provider. Laxatives should be used cautiously in chronic constipation as they are not without risk. Biofeedback training is an option for patients who have any degree of pelvic floor dysfunction.
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