Constipation in a young child as seen by X-ray. Circles represent areas of fecal matter (stool is opaque white surrounded by black bowel gas).
Constipation (also known as costiveness or dyschezia) refers to bowel movements that are infrequent or hard to pass. Constipation is a common cause of painful defecation. Severe constipation includes obstipation (failure to pass stools or gas) and fecal impaction, which can progress to bowel obstruction and become life-threatening.
Constipation is a symptom with many causes. These causes are of two types: obstructed defecation and colonic slow transit (or hypomobility). About 50% of patients evaluated for constipation at tertiary referral hospitals have obstructed defecation. This type of constipation has mechanical and functional causes. Causes of colonic slow transit constipation include diet, hormonal disorders such as hypothyroidism, side effects of medications, and rarely heavy metal toxicity. Because constipation is a symptom, not a disease, effective treatment of constipation may require first determining the cause. Treatments include changes in dietary habits, laxatives, enemas, biofeedback, and in particular situations surgery may be required.
Constipation is common; in the general population incidence of constipation varies from 2 to 30%.
The definition of constipation includes the following:
- infrequent bowel movements (typically three times or fewer per week)
- difficulty during defecation (straining during more than 25% of bowel movements or a subjective sensation of hard stools), or
- the sensation of incomplete bowel evacuation.
The Rome III criteria are widely used to diagnose chronic constipation, and are helpful in separating cases of chronic functional constipation from less-serious instances.
Constipation in children usually occurs at three distinct points in time: after starting formula or processed foods (while an infant), during toilet training in toddlerhood, and soon after starting school (as in a kindergarten) 
After birth, most infants pass 4-5 soft liquid bowel movements (BM) a day. Breast-fed infants usually tend to have more BM compared to formula-fed infants. Some breast-fed infants have a BM after each feed, whereas others have only one BM every 2–3 days. Infants who are breast-fed rarely develop constipation. By the age of two years, a child will usually have 1–2 bowel movements per day and by four years of age, a child will have one bowel movement per day.
The causes of constipation can be divided into congenital, primary, and secondary. The most common cause is primary and not life threatening. In the elderly, causes include: insufficient dietary fiber intake, inadequate fluid intake, decreased physical activity, side effects of medications, hypothyroidism, and obstruction by colorectal cancer.
Constipation with no known organic cause, i.e. no medical explanation, exhibits gender differences in prevalence: females are more often affected than males.
Primary or functional constipation is ongoing symptoms for greater than six months not due to any underlying cause such as medication side effects or an underlying medical condition. It is not associated with abdominal pain thus distinguishing it from irritable bowel syndrome. It is the most common cause of constipation.
Constipation can be caused or exacerbated by a low fiber diet, low liquid intake, or dieting.
Many medications have constipation as a side effect. Some include (but are not limited to); opioids (e.g. common pain killers), diuretics, antidepressants, antihistamines, antispasmodics, anticonvulsants, and aluminum antacids 
Metabolic & muscular
Metabolic and endocrine problems which may lead to constipation include: hypercalcemia, hypothyroidism, diabetes mellitus, cystic fibrosis, and celiac disease. Constipation is also common in individuals with muscular and myotonic dystrophy.
Structural and functional abnormalities
Constipation has a number of structural (mechanical, morphological, anatomical) causes, including: spinal cord lesions, Parkinsons, colon cancer, anal fissures, proctitis, and pelvic floor dysfunction.
Constipation also has functional (neurological) causes, including anismus, descending perineum syndrome, and Hirschsprung’s disease. In infants, Hirschsprung’s disease is the most common medical disorder associated with constipation. Anismus occurs in a small minority of persons with chronic constipation or obstructed defecation.
Voluntary withholding of the stool is a common cause of constipation. The choice to withhold can be due to factors such as fear of pain, fear of public restrooms, or laziness. When a child holds in the stool a combination of encouragement, fluids, fiber, and laxatives may be useful to overcome the problem.
The diagnosis is essentially made from the patient’s description of the symptoms. Bowel movements that are difficult to pass, very firm, or made up of small hard pellets (like those excreted by rabbits) qualify as constipation, even if they occur every day. Other symptoms related to constipation can include bloating, distension, abdominal pain, headaches, a feeling of fatigue and nervous exhaustion, or a sense of incomplete emptying.
Inquiring about dietary habits will often reveal a low intake of dietary fiber, inadequate amounts of fluids, poor ambulation or immobility, or medications that are associated with constipation.
During physical examination, scybala (manually palpable lumps of stool) may be detected on palpation of the abdomen. Rectal examination gives an impression of the anal sphincter tone and whether the lower rectum contains any feces or not. Rectal examination also gives information on the consistency of the stool, presence of hemorrhoids, admixture of blood and whether any tumors, polyps or abnormalities are present. Physical examination may be done manually by the physician, or by using a colonoscope. X-rays of the abdomen, generally only performed if bowel obstruction is suspected, may reveal extensive impacted fecal matter in the colon, and confirm or rule out other causes of similar symptoms.
Chronic constipation (symptoms present at least three days per month for more than three months) associated with abdominal discomfort is often diagnosed as irritable bowel syndrome (IBS) when no obvious cause is found.
Colonic propagating pressure wave sequences (PSs) are responsible for discrete movements of the bowel contents and are vital for normal defecation. Deficiencies in PS frequency, amplitude and extent of propagation are all implicated in severe defecatory dysfunction (SDD). Mechanisms that can normalise these aberrant motor patterns may help rectify the problem. Recently the novel therapy of sacral nerve stimulation (SNS) has been utilized for the treatment of severe constipation.
The Rome II Criteria for constipation require at least two of the following symptoms for 12 weeks or more over the period of a year:
- Straining with more than one-fourth of defecations
- Hard stool with more than one-fourth of defecations
- Feeling of incomplete evacuation with more than one-fourth of defecations
- Sensation of anorectal obstruction with more than one-fourth of defecations
- Manual maneuvers to facilitate more than one-fourth of defecations
- Fewer than three bowel movements per week
- Insufficient criteria for irritable bowel syndrome
Constipation is usually easier to prevent than to treat. Following the relief of constipation, maintenance with adequate exercise, fluid intake, and high fiber diet is recommended. Children benefit from scheduled toilet breaks, once early in the morning and 30 minutes after meals.
The main treatment of constipation involves the increased intake of water and fiber (either dietary or as supplements). The routine use of laxatives is discouraged, as having bowel movements may come to be dependent upon their use. Enemas can be used to provide a form of mechanical stimulation. However, enemas are generally useful only for stool in the rectum, not in the intestinal tract.
If laxatives are used, milk of magnesia is recommended as a first-line agent due to its low cost and safety. Stimulants should only be used if this is not effective. In cases of chronic constipation, prokinetics may be used to improve gastrointestinal motility. A number of new agents have shown positive outcomes in chronic constipation; these include prucalopride, and lubiprostone.
Constipation that resists the above measures may require physical intervention such as manual disimpaction (the physical removal of impacted stool using the hands; see Fecal impaction).
Lactulose and milk of magnesia have been compared with polyethylene glycol (PEG) in children. All had similar side effects, but PEG was more effective at treating constipation. Osmotic laxatives are recommended over stimulant laxatives.
Complications that can arise from constipation include hemorrhoids, anal fissures, rectal prolapse, and fecal impaction. Straining to pass stool may lead to hemorrhoids. In later stages of constipation, the abdomen may become distended, hard and diffusely tender. Severe cases (“fecal impaction” or malignant constipation) may exhibit symptoms of bowel obstruction (vomiting, very tender abdomen) and encopresis, where soft stool from the small intestine bypasses the mass of impacted fecal matter in the colon.
Constipation is the most common digestive complaint in the United States as per survey data. Depending on the definition employed, it occurs in 2% to 20% of the population. It is more common in women, the elderly and children. The reasons it occurs more frequently in the elderly is felt to be due to an increasing number of health problems as humans age and decreased physical activity.
- 12% of the population worldwide reports having constipation.
- Chronic constipation accounts for 3% of all visits annually to pediatric outpatient clinics.
- Constipation-related healthcare costs total $6.9 billion in the US annually.
- More than four million Americans have frequent constipation, accounting for 2.5 million physician visits a year.
- Around $725 million is spent on laxative products each year in America.