IBS is a chronic, treatable disorder that causes stomach pain, bloating, and abnormal bowel movements. People with IBS have chronic diarrhea, constipation, or both, for example several weeks of constipation followed by a few days of diarrhea. For some people, IBS involves incontinence or a feeling of incomplete evacuation. Some patients have no abdominal pain in the morning, and get stomachaches in the afternoon. Others go for two weeks without pain, and then have a day of crippling pain.
Each patient has his own pattern, says Marvin Schuster, chief of gastroenterology at the Johns Hopkins Bayview Medical Center, and director of the new Marvin M. Schuster Center for Gastrointestinal Motility and Digestive Diseases. Schuster has seen thousands of IBS patients during his 35-year career at Hopkins, and conducted a spate of studies to understand this puzzling illness.
For some people, IBS is merely an occasional nuisance. For others, says Schuster, "the pain is so intense that it dominates the patient's life." People with severe IBS can spend hours a day in the bathroom, avoid social activities for fear of losing control, and suffer a loss of dignity.
Yet there is no biochemical or laboratory test for IBS, the way there is for ulcerative colitis, or colon cancer, for example. A colonoscopy (examination of the colon through a special instrument) can reveal the fried, red tissue that is a sign of ulcerative colitis. In IBS, the lab tests come back normal, yet the colon does not function normally. Thus, physicians call IBS a "functional disorder."
Only the common cold accounts for more sick days, according to some studies.
Surveys indicate that anywhere from 8 to 17 percent of the population has IBS. Schuster and his colleagues reported that 15 percent of Americans--some 35 million people--have the syndrome. A 1993 report based on one of the most extensive studies, the U.S. Householder Survey of Functional Gastrointestinal Disorders, concluded that 9.4 percent of Americans have IBS. The surveys also reveal that women with IBS outnumber men by at least 2 to 1, and that people miss work for IBS and related disorders more than for anything else, except colds.
Yet, the studies also indicate that only between 20 and 50 percent of people with IBS seek medical help. "There's no bleeding, no fever to cause alarm," notes Schuster.
Nancy Norton, 47, a former patient of Schuster's, is a case in point. When she was a teenager, Norton started having horrible cramps and diarrhea, which got worse over the years. By the time she was in her 30s, she was having symptoms two days out of three. She would cart around a bottle of Pepto Bismol. "People used to joke that I was like a walking pharmacy," says Norton. "I remember not wanting to go to a Bucks basketball game for fear of not being able to find a bathroom in the stadium."
Norton did not find out about IBS until about 10 years ago. Now president of a nonprofit patient education and advocacy organization called the International Foundation for Functional Gastrointestinal Disorders, Norton gives seminars on IBS that attract hundreds of people. "We hear repeatedly, 'I thought I was the only one,'" she says.
Getting the right diagnosis can be difficult.
"Old-time doctors used to tell IBS patients the problem was all in their mind," says Schuster. Medical terms once used for IBS-- "spastic colon," "nervous colon," or "unstable colon"--even connoted a neurosis, which was "very disillusioning to patients," he says.
The fact is, "irritable bowel syndrome is an illness," just as diabetes and heart disease are illnesses," says Schuster. (That said, it is also true that stress triggers about half of the episodes of IBS. More on that later.)
In diagnosing IBS, a physician should first rule out other diseases that share similar symptoms, such as ulcerative colitis, colon cancer, diverticulosis, parasites, and dysentery and other infectious illnesses, says Schuster. Once those conditions have been excluded, a brief checklist called the Rome Criteria for IBS is used to diagnose the condition.
If you answer "yes" to both of the questions below, you could have IBS. And if you have symptoms, it is important to have a physician examine you.
During the past three months have you experienced continuous or recurrent symptoms of:
1. Abdominal pain or discomfort which is: relieved by defecation? and/or associated with a change in frequency of stool? and/or associated with a change of consistency of stool? andThe gut is like a well-synchronized factory.
As food passes through the digestive tract, it is torn, battered, and compacted by the stretching and contracting of the muscles lining the tract. Each region of the digestive system performs a different type of muscular movement.
Starting in the esophagus, waves of muscular contraction move downward like rings sliding down a pole. Peristalsis, as the movement is called, pushes food down and into the stomach. "The esophagus is essentially a transit tube," says Schuster. No digestion occurs here.
The stomach muscles then work like a pendulum that pushes food back and forth, back and forth, bathing it in digestive juices that break it into grain-size pieces (about one millimeter).
Pendular contractions continue in the 21 feet of tubing called the small intestine, or bowel. "Here is where almost all digestion and absorption of nutrients takes place," says Schuster. "If food just went rapidly through, you would not absorb enough nutrients." In between meals, peristaltic waves that occur every 90 to 120 minutes sweep out any remaining particles of food.
Then, it's on to the colon, or bowel. "The colon is made mainly for storage," says Schuster. "It absorbs water and salts, and solidifies the contents into solid waste." The majority of the time, the colon is quiescent, barely moving a muscle. But following a meal, the colon periodically contracts at different points along its length. Contractions will occur 10 centimeters apart, at 10-minute intervals, for example. These segmenting contractions slow down the flow of waste, and keep it in contact with the bowel wall, allowing water to be absorbed. Finally, organized peristaltic contractions push the bowel contents through.
Transit time through the entire 30-foot system, from mouth to anus: between 24 and 72 hours.
In IBS, the factory is out of sync.
Schuster and his colleagues conducted a series of studies in which volunteers wore tiny pressure transducers that recorded the pressure of the muscles lining their colon and rectum. Recordings were made over a 24-hour period, while volunteers went about their normal daily routines.
The researchers found that many IBS patients have disorganized and significantly more vigorous contractions. The muscles tend to spasm. "There's a more prolonged contraction, over a larger area," says Schuster. "It's like having a Charlie horse in the gut."
The Hopkins team found that while healthy volunteers had between six to eight peristaltic contractions in their colon within a 24-hour period, IBS volunteers who tended to be constipated had almost none, and volunteers who frequently had diarrhea had as many as 25 peristaltic contractions per day.
There is no agreement as to the cause of IBS.
Schuster's experiments indicate that spastic contractions cause the abdominal pain of IBS. But that is far from the end of the story. For one thing, some IBS volunteers do not appear to have spasms--at least not detectable ones. Also, spasms can occur without triggering pain (as in healthy people who experience the painless spasms of gas bubbles). And even if spasms do trigger IBS pain, what triggers the spasms? The illness appears to be a complicated soup, and possibly one with many ingredients. While researchers have not found a definitive explanation of the syndrome's underpinnings, they have intriguing leads.
a) Many or all people with IBS have a much lower threshhold for intestinal pressure or pain, says Schuster. So an innocuous gas bubble for most people might send an IBS patient running to the medicine cabinet.
In a series of studies, Schuster and his colleagues recorded volunteers' response to gradually increasing rectal pressure. The experimental set-up mimics what happens as gas or waste material passes through the colon and rectum. A balloon placed in a volunteer's upper rectum is gradually distended, and the volunteer is periodically asked to rate the level of pain.
Volunteers without IBS reported moderate pain when the balloon volume reached about 160 milliliters, reports Schuster. Patients with IBS experienced the same level of pain at only about 60 ml. In IBS, suggest the researchers, the nerve endings in the rectum and perhaps throughout the gastrointestinal tract may be more sensitive.
b) Physicians now know that stress and anxiety do not cause IBS, but they can aggravate its symptoms. But this wasn't always the case. Consider the experience of Keith Fellerman, 67, a prominent engineer and space scientist who was a key figure in the Mercury, Apollo, and Gemini missions of the 1960s. It was stimulating work, and nothing could beat the thrill of seeing three years' labor rocket off the launchpad. But stress was inherent in the job, and it took a toll on Fellerman. "When I was under tension, my stomach would just explode," leading to three- and four-day bouts of diarrhea, he recalls. Fellerman's doctor diagnosed spastic colon, and suggested that the condition was part and parcel of his type A personality. Now a patient of Hopkins gastroenterologist Ted Bayless, Fellerman says it is a relief to know what is wrong, and has found a combination of medications that ease his symptoms.
Anyone who has ever had butterflies before giving a speech or a bellyache before taking an exam knows that the emotions and the intestines are interwoven. This mind-gut relationship was scientifically explored in a classic set of experiments that were conducted in the late 1940s and early '50s by Cornell University gastroenterologist Tom Almy. While monitoring the rectal mucosa of medical student volunteers through a proctoscope, Almy and his collaborators would make a number of potentially embarrassing or anxiety-provoking remarks. For example, the researchers would say, "I heard you flunked the exam yesterday," or whisper, "Colon cancer."
In response, the rectal mucosa would turn beefy red, the way some people blush when they are embarrassed, explains Bayless, who was an Almy protege. Once the investigators explained the "hoax" to the volunteers, the mucosa returned to its normal color.
The experiments would be ethically suspect today, says Bayless, but they gave some credence to the saying, "My stomach is tied in knots." Even in healthy volunteers, the gut and the emotions are closely linked; in IBS, the connection may simply be tighter.
Since Almy's experiments, researchers have begun to elucidate this relationship. They have found, for example, that every neurotransmitter in the brain also occurs in the gut, says Schuster.
Some physicians believe that IBS patients do not have an actual disease, but are simply at the far end of a continuum of vulnerability to perturbations in intestinal motility. "Is IBS a disease any more than skin problems are for people who sunburn more easily?" asks Hopkins gastroenterologist Thomas Hendrix. "I think an awful lot of what we call IBS is a variation of intestinal function analogous to skin sensitivity. The intestinal response to environmental stresses is simply more exaggerated." For some people, stress causes headaches. Others are gut responders. In any case, the body is telling us "we're getting to the end of our rope," says Hendrix.
c) In IBS, the smooth muscle cells of the gut may be dancing to a different rhythm.
In much the same way that brain cells produce electrical activity that can be measured through electroencephalograms, the gut's smooth muscle cells produce electrical activity that can be measured with electrodes, says Michael Crowell, director of GI Physiology and Motility at the Schuster Center.
The muscle electrical activity oscillates at a set rhythm. In the healthy colon, this rhythm is 6 cycles per minute most of the time; 10 percent of the time it is 3 cycles per minute. Researchers at the University of Pennsylvania found that about 40 percent of the time, IBS patients have a rhythm of 3 cycles per minute.
"What the relevance is, I couldn't tell you," says Crowell. "It's not clear how the slower rhythm would affect contractions." At this point, the findings are no more than an intriguing observation. The unusual rhythm could be a marker for IBS, says Crowell, but it is not necessarily the underlying cause of its symptoms. Furthermore, Crowell and his colleagues were not able to replicate the findings.
d) Other hypotheses. Scientists have proposed that an as-yet-undetected inflammatory process underlies IBS. Another hypothesis is that food sensitivities trigger IBS symptoms. But in both cases, scant research supports these ideas, Schuster says.
e) Finally, the reason IBS is so complex may be that it is not just one thing. While some IBS patients have spastic contractions that cause pain, others do not appear to have spastic contractions. While many IBS volunteers are hypersensitive to gut sensations, as shown by the balloon distension tests, others tolerate the pressure as well as healthy volunteers do. "The whole point is that there appears to be subgroups of IBS," says Crowell. "IBS is a real quagmire."
There's no magic bullet for IBS.
Treatment for IBS often comes "as a package," says Schuster. Patients may need to try a combination of the following measures:
IBS is not colitis or cancer, and IBS patients do not have a greater risk of developing those illnesses. However, Schuster cautions that patients should be alert to any changes in their symptoms, which could indicate a new illness.
For more information contact the
International Foundation for Bowel DysfunctionFollow this link for Marvin Schuster's insights into helping patients to maintain their dignity
Melissa Hendricks is the magazine's senior science writer.
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