Constipation is the painful or difficult passing of food product waste (stool) through the anus. Stool may be hard, dry and painful to pass, or a person may need to strain in order to have a bowel movement.  It may feel as if the bowels still need to be emptied, even after stool has been passed. Constipation may be accompanied by other symptoms, including gas, nausea, rectal pressure and abdominal pain, cramping or distention.

During normal digestion, food moves from the stomach to the small intestine, where nutrients are absorbed. By the time it gets to the colon (large intestine), only the waste material remains. The colon absorbs water from the waste and passes the stool along via muscle contractions (peristalsis) to the rectum at the end of the digestive tract.

Constipation occurs when waste material moves too slowly through the intestines and too much water is absorbed and stool becomes hard and difficult to pass.

The longer waste stays in the intestines, the more water is taken from it and reabsorbed into the body.

Many people believe that it is necessary to have a bowel movement every day. The belief that all waste must be eliminated from a person’s body in order to maintain health or cleanliness is also common. However, both are untrue. The frequency of bowel movements can vary greatly from person to person, and can range from three times a day to three times a week. The natural firmness of stool can also vary from person to person. Passing stool less than three times a week may indicate constipation. 

At some point in their lives, most people experience constipation. It is one of the most common gastrointestinal complaints in the United States. Approximately 3 million Americans have frequent constipation, according to the National Institutes of Health (NIH). 

Constipation is reported most often among adults age 65 and over. Seventy-five percent of elderly hospitalized patients and nursing home residents use laxatives to help regulate their bowel movements. Older adults may be overly concerned with a daily bowel movement, leading them to believe they have constipation when they do not. Older adults are also likely to take constipation-causing medications, have decreased levels of physical activity, and low-fiber, high-fat diets. All of these factors can contribute to constipation.

Constipation is also common following childbirth or surgery. People who learn to withhold their bowel movements by not acting on urges to defecate may also experience constipation. This may occur in children during toilet training, in adults with concerns about using public toilets or for other, varied reasons.

Constipation may be acute or chronic. The symptoms of acute constipation tend to begin suddenly and are very obvious. Chronic constipation occurs gradually and may last for longer periods of time. Chronic constipation can continue for months or years.