Irritable bowel syndrome (IBS)—also called irritable or spastic colon—is a common functional intestinal disorder characterized by recurrent abdominal discomfort and abnormal bowel function. The discomfort often begins after eating and goes away after a bowel movement. The symptoms can include cramps, bloating, constipation, diarrhea, and a feeling of incomplete emptying.
IBS occurs in about one in five Americans, more commonly in women, and more often at times of emotional stress. It usually begins in late adolescence or early adult life and rarely starts after the age of 50. In severe cases, it can result in missed work days and curtailment of social activities. Although effective help is available, many people with IBS are too embarrassed, pessimistic, or afraid to seek medical care. Even worse, some people who consult a doctor receive insufficient guidance and conclude that nothing further can be done for them.
Why Symptoms Occur
During normal digestion, foods are broken down in the stomach and small intestine so that their nutrients can be absorbed into the body. Undigested or partially digested portions—mostly in liquid form—then enter the large intestine (colon) where most of the water is reabsorbed. Movement through the intestines results from peristalsis, a wavelike contraction of muscles in the intestinal walls that propel their contents forward. When all is well, the end result is stool that is solid but soft enough to be excreted easily.
Diet, eating habits, stress, and various environmental factors can disrupt the normal function of the intestines. If the intestines squeeze too hard or not enough, the partially digested food can travel too rapidly or too slowly through the digestive system. Movement that is too fast will result in diarrhea, because not enough water is reabsorbed. Movement that is too slow can result in constipation, because too much water is absorbed. Overly hard squeezing (spasm) can result in cramps. However, the diarrhea of IBS can also occur without pain.
IBS symptoms occur after eating because of the gastrocolic reflex—increased movement of the intestinal contents in response to food entering the stomach. The strength of this reflex can be influenced by the volume and temperature of the food and the number of calories. Large meals (particularly high-fat meals) and large amounts of cold beverages can trigger IBS attacks.
A thorough history and physical examination should be obtained. The extent of further evaluation depends on the patient’s age, general health, and symptoms. If symptoms have been present a long time and have a typical pattern, the doctor may rely mainly on the patient’s description to diagnose IBS. If symptoms are recent in origin, testing may be needed to be certain that an infection, inflammation, or tumor is not responsible for the symptoms. The tests may include blood tests, stool tests, x-ray examinations, and endoscopy (examination of the colon with a hollow tubular instrument inserted from below).
The first step in managing IBS should be to identify what triggers the symptoms. The factors to consider include food intolerances, eating habits, dietary factors, emotional stress, exercise habits, use of laxatives, and vitamin C intake. It may help to keep a diary that relates symptoms to daily activities.
Many people with IBS have difficulty digesting lactose (milk sugar). This results from a shortage of lactase, an enzyme normally produced by cells lining the small intestine. Lactase breaks down milk sugar into simpler substances that are absorbed into the bloodstream. When there is not enough lactase, undigested lactose can ferment in the large intestine and cause nausea, cramps, bloating, flatulence, and diarrhea that begin about 30 minutes to 2 hours after consuming lactose-containing foods. The severity of symptoms varies with the amount of lactose the individual can tolerate. To determine whether lactose intolerance is a factor in IBS, the patient can experiment to see whether symptoms are related to milk intake. Laboratory testing may also be useful. If lactose intolerance is significant, lactase drops or tablets can be added to ordinary milk, low-lactose products can be substituted, or dairy products can be avoided (in which case the patient should take calcium supplements).
Bloating or excessive gas can also be related to eating habits and diet. Drinking carbonated beverages can introduce gas into the intestines and cause abdominal pain. Eating or drinking rapidly, chewing gum, smoking, nervously gulping air, or wearing loose dentures can cause some people to swallow a large amount of air, some of which reaches the large intestine. Gas can also be produced by such foods as beans, onions, broccoli, and cabbage. Eating more slowly or minimizing gas-forming foods may help.
Since caffeine can increase intestinal motility, people with IBS should avoid or minimize the use of caffeine-containing beverages such as coffee and caffeinated colas. Fructose or sorbitol (a sugar substitute) can induce diarrhea in some people. Since vitamin C supplements of 1 gram/day or more can cause diarrhea, patients with chronically loose stools should be advised to stop taking them.
Unnecessary delay in defecation should be avoided. When an urge is felt, leaving the stool in the colon may contribute to constipation because the longer the contents remain, the more fluid may be absorbed. Use of certain laxatives can perpetuate constipation because the large intestine can become dependent on them. People with IBS should not take strong laxatives.
Increasing the fiber content of the diet or taking a stool softener such as methylcellulose or psyllium may help regulate bowel movements and reduce both constipation and diarrhea. Increasing dietary fiber should be done gradually to give the body time to adjust. Prescription drugs are available to slow the movement of food through the intestines or to relieve intestinal spasm.
In patients with abdominal pain, medication, a hot bath, or a hot water bottle applied to the abdomen may relieve an acute attack. Antispasmodics can also prevent attacks. If a certain type of activity is known to trigger an attack, taking an antispasmodic drug beforehand may prevent trouble. If modifiable sources of stress can be discovered, resolving them may help. Regular exercise can also help to normalize bowel action.
This article was posted on June 7, 2000.