Constipation! What is it?

Constipation 

The colon of the large intestine has four regions: the as­cending colon, the transverse colon, the descending colon, and the sigmoid colon. Water is removed from the nondigestible remains that enter the ascending colon from the small intestine. At this point, bacteria begin their action; they use cellulose as an energy source as they produce fatty acids and vitamins that can also be used by their host. They also re­lease hydrogen gas and sulfur-containing compounds that contribute to human flatulence (gas). Feces, which consist of nondigested remains, bacteria, and sloughed-off intestinal cells, begin to form in the transverse colon. From there, they are propelled down the descending colon toward the rectum by periodic, firm contractions. When sufficient feces are in the rectum (130-200 grams), a defecatory urge is felt. The defeca­tion reflex contracts the rectal muscles and relaxes the internal anal sphincter, a ring of muscle that closes off the rectum. Then, feces move toward the anus. A pushing motion, along with relaxation of the external anal sphincter, propels feces from the body. Since these activities are under voluntary con­trol, it is possible to control defecation. 

Defecation normally occurs from three times a week to three times a day; therefore, some variation in occurrence is nothing to worry about. However, if the frequency of defecation declines and if defecation becomes difficult, then constipation is present. If constipation is a continuing problem, a physician can help record the movement of materials through the large in­testine via several tests. The patient swallows about 20 small markers that will show up on an X ray. At intervals during the following week, X rays are taken, and the number and locations of the markers are noted. If muscle contraction of the intestinal wall is insufficient, the markers move slowly along their course. Injured nerves, certain drugs, and prolonged overuse of stimula­tory laxatives can bring about this difficulty. On the other hand, markers may move normally at first and then slow down con­siderably in the descending colon and rectum. Habitual disre­gard of the defecatory urge may have caused this problem, or a cancerous polyp might be obstructing normal movement. If the former is the case, it is possible to retrain the rectum to work properly. Sitting on the toilet about 20 minutes each morning can encourage a return of the reflexes that have disappeared, but straining is not recommended. 

Temporary constipation due to traveling, pregnancy, or medication can sometimes be relieved by increasing dietary fiber, drinking plenty of water, and getting moderate amounts of exercise. The use of oral laxatives (agents that aid emptying of the intestine) is a last resort. Bulk-forming laxatives, such as those that contain bran, psyllium, and methyl cellulose, are considered best because they promote the defecation reflex. Laxatives that contain osmotic agents, such as carbohydrates or salts (lactulose, milk of magnesia, or Epsom salts), cause water to move into rather than out of the colon. Stool soften­ers (mineral oil or those that contain docusate) should be used sparingly. Mineral oil reduces the absorption of fat-soluble vitamins, and docusate can cause liver damage. Laxatives that contain chemical stimulants (such as phenolphthalein in Ex­Lax and Feen-A-Mint) can damage the defecation reflex and lead to a dependence on their use. Aside from laxatives, rectal suppositories are sometimes helpful in providing lubrication. 

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