Bowel Movement Disorders

Bowel Movement Disorders

Bowel (intestinal) function varies greatly not only from one person to another but also for any one person at different times. It can be affected by diet, stress, drugs, disease, and even social and cultural patterns. In most Western societies, the normal number of bowel movements ranges from two or three a week to as many as two or three a day. Changes in the frequency, consistency, or volume of bowel movements or the presence of blood, mucus, pus, or excess fatty material (oil, grease) in the stool may indicate a disease.

Constipation is a condition in which a person has uncomfortable or infrequent bowel movements.

A person with constipation produces hard stools that may be difficult to pass. The person also may feel as though the rectum has not been completely emptied. Acute constipation begins suddenly and noticeably. Chronic constipation, on the other hand, may begin insidiously and persist for months or years.

Often the cause of acute constipation is nothing more than a recent change in diet or a decrease in physical activity, for example, when a person stays in bed for a day or two during an illness. Many drugs - for example, aluminum hydroxide (common in over-the-counter antacids), bismuth salts, iron salts, anticholinergics, antihypertensives, narcotics, and many tranquilizers and sedatives - can cause constipation. Acute constipation occasionally may be caused by serious problems such as an obstruction of the large intestine, poor blood supply to the large intestine, and nerve or spinal cord injury.

Too little physical activity and too little fiber in the diet are common causes of chronic constipation. Other causes include an underactive thyroid gland (hypothyroidism), high blood calcium levels (hypercalcemia), and Parkinson's disease. A decrease in the contractions in the large intestine (inactive colon) and discomfort during defecation also lead to chronic constipation. Psychologic factors are common causes of acute and chronic constipation.

When a disease is causing constipation, the disease must be treated. Otherwise, constipation is best prevented and treated with a combination of adequate exercise, a high-fibre diet, and the occasional use of appropriate medications.

Vegetables, fruits, and bran are excellent sources of fiber. Many people find it convenient to sprinkle two or three teaspoons of unrefined miller's bran or high-fibre cereal on fruit two or three times a day. To work well, fibre must be consumed with plenty of fluids.

Many people use laxatives to relieve constipation. Some are safe for long-term use; others should be used only occasionally. Some are good for preventing constipation; others can be used to treat it.

Bulking agents (bran, psyllium, calcium polycarbophil, and methylcellulose) add bulk to the stool. The increased bulk stimulates the natural contractions of the intestine, and bulkier stools are softer and easier to pass. Bulking agents act slowly and gently and are among the safest ways to promote regular bowel movements. These agents generally are taken in small amounts at first. The dose is increased gradually until regularity is achieved. People who use bulking agents should always drink plenty of fluids.

Stool softeners, such as docusate, increase the amount of water that the stool can hold. Actually, these laxatives are detergents that decrease the surface tension of the stool, allowingwater to penetrate the stool more easily and soften it. The increased bulk stimulates the natural contractions of the large intestine and helps the softened stools to move more easily out of the body.

Mineral oil softens the stool and facilitates its passage out of the body. However, mineral oil may decrease the absorption of certain fat-soluble vitamins. Also, if a person-for instance, someone who is debilitated-accidently inhales (aspirates) mineral oil, serious lung irritation can develop. Plus, mineral oil seeps from the rectum.

Osmotic agents pull large amounts of water into the large intestine, making the stool soft and loose. The excess fluid also stretches the walls of the large intestine, stimulating contractions. These laxatives consist of either salts-usually phosphate, magnesium, or sulfate or sugars that are poorly absorbed - for example, lactulose and sorbitol. Some osmotic agents contain sodium. They may cause fluid retention in people with kidney disease or heart failure, especially when given in large or frequent doses. Osmotic agents containing magnesium and phosphate are partially absorbed into the bloodstream and can be harmful in people with kidney failure. These laxatives, which generally work within three hours, are better for treating constipation than for preventing it. They are also used to clear stool from the intestine before X-rays of the digestive (gastrointestinal) tract are taken and before colonoscopy (an examination of the large intestine using a flexible viewing tube) is performed.

Stimulant laxatives directly stimulate the walls of the large intestine, causing it to contract and move the stool. These laxatives contain irritating substances such as senna, cascara, phenol-phthalein, bisacodyl, or castor oil. They generally cause a semisolid bowel movement in six to eight hours but often cause cramping as well. In suppositories, these laxatives often work in 15 to 60 minutes. Prolonged use of stimulant laxatives can damage the large intestine. Also, people can become addicted to stimulant laxatives, developing lazy bowel syndrome, which creates a dependency on the laxatives. Stimulant laxatives are often used to empty the large intestine before diagnostic procedures and to prevent or treat constipation caused by drugs that slow the contractions of the large intestine, such as narcotics.

Psychogenic Constipation
Many people believe they have constipation if they do not have a bowel movement every day. Other people think they have constipation if the appearance or consistency of their stool seems abnormal to them. However, daily bowel movements are not necessarily normal, and less frequent bowel movements do not necessarily indicate a problem unless they represent a substantial change from previous patterns. The same is true of the color and consistency of stool; unless there is a substantial change in them, the person probably does not have constipation.

Such misconceptions about constipation can lead to overzealous treatment, especially the long-term use of stimulant laxatives, irritant suppositories, and enemas. Such treatment can severely damage the large intestine or induce lazy bowel syndrome and melanosis coli (abnormal changes in the lining of the large intestine caused by deposits of a pigment).

Before making a diagnosis of psychogenic constipation, a doctor first ensures that an underlying physical problem is not causing irregular bowel movements. Diagnostic tests, such as a sigmoidoscopy (an examination of the sigmoid colon using a flexible viewing tube) or a barium enema, may be needed. If there's no underlying physical problem, the person needs to accept the existing pattern of bowel movements and not insist on a more regular pattern.

Colonic Inertia
Colonic inertia (inactive colon) is a decrease in contractions in the large intestine or an insensitivity of the rectum to the presence of stool, resulting in chronic constipation.

Colonic inertia often occurs in people who are elderly, debilitated, or bedridden, but it also occurs in otherwise healthy younger women.

The large intestine stops responding to the stimuli that usually cause bowel movements: eating, a full stomach, a full large intestine, and stool in the rectum. Drugs used to treat medical conditions frequently cause or worsen the problem, especially narcotics (such as codeine) and drugs with anticholinergic properties (such as amitriptyline for depression or propantheline for diarrhea). Colonic inertia sometimes occurs in people who habitually delay defecation or who have used laxatives or enemas for a long time.

Constipation is a long-term, day-to-day problem; the person may or may not have abdominal discomfort. Often a doctor finds the rectum filled with soft stool, even though the person has no urge to defecate and can do so only with difficulty.

People with this condition may develop fecal impaction, in which the stool in the last part of the large intestine and rectum hardens and blocks the passage of other stool. This blockage leads to cramps, rectal pain, and strong but futile efforts to defecate. Often, watery mucus material oozes around the blockage, sometimes giving the false impression of diarrhea.

For colonic inertia, doctors sometimes recommend suppositories or enemas with two to three ounces of water, water and salts (saline enemas), or oils such as olive oil. For fecal impaction, laxativesusually osmotic agents are needed as well. Sometimes a doctor or nurse must remove hard impacted stool with a gloved finger or probe.

People who have colonic inertia should try to defecate daily, preferably 15 to 45 minutes after a meal because eating stimulates a bowel movement. Exercise often helps.

Dyschezia is difficulty in defecating caused by an inability to control the pelvic and anal muscles. Having a normal bowel movement requires relaxation of the muscles in the pelvis and the circular muscles (sphincters) that keep the anus closed. Otherwise, efforts to defecate are futile, even with severe straining. People with dyschezia sense the need to have a bowel movement, but they can not have one. Even stool that is not hard may be difficult to pass.

Conditions that can interfere with muscle movement include pelvic floor dyssynergia (a disturbance of muscle coordination), anismus (a condition in which the muscles fail to relax or paradoxically contract during defecation), a rectocele (hernia of the rectum into the vagina), enterocele (hernia of the small intestine into the rectum), rectal ulcer, and rectal prolapse.

Treatment with laxatives is generally unsatisfactory. Currently, relaxation exercises and bio-feedback are being tested for pelvic floor dyssynergia and show much promise. Surgery may be needed to repair an enterocele or a large rectocele. Constipation can become so severe that stool must be removed by a doctor or nurse using a gloved finger or probe.

Additional Resources:
Bowel Movement Problems: Queensland Government
Stomach and Bowel Disorders: Medicdirect

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