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 Irritable Bowel Syndrome (IBS)

Gary M. Gray, M.D.

Irritable bowel syndrome (IBS), also known as spastic colon or functional bowel syndrome, is a very common condition, affecting as many as 10 or even 20 percent of adults in the Western world.1 IBS symptoms usually include moderately intense abdominal pain, most often in the left lower area, and bouts of "loose bowels," or multiple stool passages over several days, alternating with periods of infrequent stool output (constipation). From time to time, many of us have these symptoms. It's only when they recur regularly and last several weeks that one should begin to consider they might be caused by IBS.

IBS is usually diagnosed in young adulthood and is at least twice as common in women as in men. Although most people with IBS simply accept their symptoms as a nuisance and never seek medical attention,2 it is still the most common gastrointestinal problem seen by family doctors and internists.3

Women, more than men with IBS, are more likely to complain of constipation and abdominal bloating4 but both often feel a sensation of fullness and distension in the abdomen.5 The bloating sensation is rarely associated with actual gas retention or passing unusually large amounts of gas.6

Though sufferers report characteristic multiple stool passages, it is not true "diarrhea" because the stools tend to be small in volume. They are passed in relatively rapid succession, typically in the early morning, over a period of 30 minutes to an hour. A mucus coating is often observed but there is no visible blood.

An important distinction is whether there is a brief "squirt" of stool or a "gush" that lasts for several seconds. The first is typical of IBS, while the second would point to an infection, or perhaps an inflammatory condition.

Before the diagnosis of IBS can be made, your physician will search for other possible causes of the altered stool output. A flexible sigmoidoscopy and barium enema, or a full colonoscopy should be done. These flexible fiberoptic instruments enable the doctor to exclude infection or inflammatory bowel disease (ulcerative colitis or Crohn's disease), both of which can cause similar symptoms. Because inflammation of the colon can sometimes be difficult to detect even with these methods, the doctor will often take a tiny piece of tissue, a biopsy, for microscopic evaluation.

Associations and Risk Factors
More than one-third of people with IBS have symptoms that are also typical of functional, or "non-ulcer," abdominal discomfort ("dyspepsia").7 In contrast to dyspepsia, abdominal discomfort in IBS is not usually associated with ingestion of meals.

IBS is associated with a variety of seemingly unrelated conditions in ways that are not well understood. For example, those with recurring episodes of abdominal pain in childhood and adolescence are at greater risk of developing IBS as adults.8 Psychologically depressed patients are 10 times more likely to develop IBS.9 Panic disorder,10 schizophrenia11, sexual dysfunction and the occurrence of physical or sexual abuse during childhood12,all seem to be associated in some way with the development of IBS.13

Some studies point to gastroenteritis, caused by infection, as a pre-existing cause of IBS.14,15

IBS, Stress and Pain Perception
IBS seems to be related, as well, to other psychological factors. A recent study showed that when asked to solve mental arithmetric problems, a higher proportion of IBS patients (29%) than non-IBS participants (4%) displayed certain distinctive brain wave [electroencephalo-graphic (EEG) patterns].16 This suggests that IBS may be related to how the brain handles psychological stress17,18,19 IBS sufferers seem also to have a lower pain threshold for perceiving abdominal pain when compared to individuals who don't have IBS. IBS patients, for example, often experience unusual discomfort when undergoing a colonoscopy or barium enema X-ray.20,21,22

Treatment
Because IBS covers quite a few symptoms that vary widely from patient to patient, your physician will need to identify which subtype of IBS you have. The three main subtypes are diarrhea-predominant, constipation-predominant, and pain and bloating-predominant. Table 1 (below) shows how treatment approaches differ, depending on which subtype is involved.

Table 1. Treatment of IBS by Type of IBS

Diarrhea-predominant
  • Antidiarrheal agents [loperamide (Immodium®) or diphenoxylate with atropine (Lomotil®)]
  • Tincture of Opium
  • Antispasmotics
  • High fiber supplements (Metamucil®, Citrocel®, Fibercon®)
  • Tricyclic drugs
Constipation-predominant
  • High fiber diet
  • Increased physical activity
  • Osmotic-active drugs
  • Tricyclics
  • Other Drugs
  • Pain management (with psychiatric input)
Pain-predominant
  • Antispasmotics
  • Avoid narcotics
  • Increased physical activity

Dietary Fiber
The treatment of patients with IBS is based largely on trial and error. The most common therapy is increasing the daily intake of the non-digestible carbohydrates, or fiber, that are present in vegetables and partially processed grains.23 Wheat bran, raw fruits and vegetables, or those that are only partially cooked, serve as important sources and have been widely recommended, especially for the constipation-predominant form of IBS. The goal is to eat 12 grams of fiber per day.

Most patients find it difficult to consume this much fiber in food and turn to commercial preparations such as Metamucil®, Citrocel® or Fibercon®) as a fiber supplement. These are usually taken in relatively small quantities, (say, a teaspoon), once to three times daily. However, it often takes far more fiber than this -- as much as three tablespoons three times daily -- to provide any relief of constipation caused by IBS. Another problem is that although patients who increase their fiber intake often find an increase in stool volume, they may feel an even greater bloating sensation. For some patients with diarrhea-predominant IBS, increased fiber intake, particularly when it comes in the form of bran, may bring an increase in the bloating sensation with little or no reduction in stool frequency.

Anti-diarrheal Drugs
For the person with the diarrhea-predominant form of IBS, who is having a major bout of loose bowel movements, the best treatment can be antidiarrheal agents such as loperamide (Immodium®) or diphenoxylate with atropine (Lomotil®). If the IBS sufferer has an extremely severe sense of urgency to pass gas and loose stools requiring numerous trips to the bathroom each day, tincture of opium may be beneficial when other antidiarrheal drugs have failed.

Specialized Drug Therapy
No single drug has been consistently effective in treating the many symptoms and varieties of IBS, although there is an ever-increasing range of specialized drugs which can be effective. Whether to try these and under what circumstances is something that individual IBS sufferers should discuss directly with their physician.24,25,26,27,28,29,30,31

Expectations for the Therapy of IBS in the Next Few Years
Though common, IBS is often a very difficult disease to treat. The good news about IBS is that there is now considerable interest among medical investigators in identifying the molecular basis of IBS. Hopefully, we can look forward both to a better understanding of IBS and better treatments in the near future.

August 2000 Email this article to a friend

References
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