Irritable bowel syndrome (IBS) poses something of a dilemma: Physicians readily recognize when a person has it, but describing a consistent pattern of symptoms is nearly impossible. People with an irritable bowel may complain of cramping pain in any part of the abdomen, feeling bloated, gas, constipation, as well as diarrhea and excessive mucus in the stool. Often, the same person may complain of either constipation or diarrhea, later experience another symptom, and then alternate again. The symptom(s) that occurs most frequently also will vary from individual to individual.
Worldwide, IBS affects about one in seven to 10 people. Over 22 million Americans suffer from this condition, which is second only to the common cold as a cause of absenteeism from work. Reports indicate that three times as many women as men are afflicted with irritable bowel syndrome. Researchers speculate that the fluctuation of reproductive hormones during menstrual cycles may increase the occurrence of these symptoms. The truth is that the cause or causes of IBS are not well understood at all. It is very likely that multiple factors are involved.
You can guess at the number of disorders that researchers thought produced IBS by ticking off the names given to this problem over the years. Irritable bowel syndrome has been called psychogenic colitis, mucous colitis, or just plain colitis – suggesting that there is inflammation (or “-itis”) of the lining of the colon. This is a misnomer because no inflammation is present.
Perhaps, as some have suggested, if there is an inflammation it is due to a bowel infection. Nowadays, most physicians do not believe infection is a factor, though they do think that some irritation of the small or large intestine is involved. At one time intolerance to certain foods and food allergies were considered major factors in IBS. While we know that this is a cause, it is unlikely to be the only cause.
Irritable bowel syndrome has also been called psychogenic colitis, or the nervous gut, in the belief that psychologic distress – nerves, depression, or anxiety – causes the onset of symptoms.
Another name for IBS was spastic colitis or spastic colon. This referred to the painful contractions a sufferer would feel inside his or her lower gut. These abnormal, uncoordinated contractions, or dysmotility, may be linked to a change in the firing of electrical signals that control muscular activity. This pacemaker mechanism is similar to the system controlling the contraction of heart muscle. And as with the heart, an abnormal pattern or rhythm—a dysrhythmia—may develop.
Recent research has strongly suggested a central role for abnormal gut sensitivity. According to this view, motility in the gut is normal. However, the nerve endings in the lining of the small and large intestines are unusually sensitive and will react abnormally to even ordinary events such as eating. For example, when ingested food reaches the bowel, the gut wall expands (or distends), causing the nerves to trigger exaggerated patterns of muscular activity. As a result, sometimes, a meal may be followed almost immediately by cramps, and soon after by a bowel movement. Other stimuli that can cause this over-reacting include stressful events, taking certain medications, drinking milk or swallowing too much air.
In any person with irritable bowel syndrome, it is difficult to pin down the cause because each time, the underlying disorder, or combination of contributing disorders, will probably be different. Thus, there is no specific test you can take that will tell whether or not you have IBS — and no procedure that will allow the physician to see what is wrong. In technical language, that means IBS is a functional disorder.
Nevertheless, your physician will frequently order tests because your symptoms might suggest the presence of another, more serious disease. He or she will be particularly alert to this possibility if you have rectal bleeding, weight loss, or severe and/or persistent pain. After analyzing the results of appropriate tests, the physician will be able to reassure you, for example, that you do not have cancer.
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