Irritable bowel syndrome (IBS) is the most common diagnosis (25-50%) given to people referred to stomach and intestine specialists. It is reported to affect between 10-15% of people in the U.S. However, it cannot be diagnosed by any specific tests. It is diagnosed by criteria. The criteria are called the Rome II diagnostic criteria because a group of doctors meet periodically to establish rules for labeling intestinal conditions that have no diagnostic tests.

These conditions are called syndromes because they don't meet the definition for a disease. They don't have a specific known cause and/or diagnostic test(s). They are often referred to as "functional" problems. The cause of the functional problem in IBS is not known. By definition there is no abnormality that can be seen on a biopsy, x-ray, blood or stool test. The diagnosis is made by applying criteria after exclusion of other conditions or diseases of the intestine. There is not a universally agreed upon consensus for what constitutes an adequate evaluation to exclude other causes.

For IBS the criteria required to make the diagnosis is the presence of abdominal pain or discomfort that has been present for at least 3 months in past year (not necessarily consecutively) and has at least two of three of the following features:

1. The pain or discomfort is relieved with a bowel movement.

2. The beginning of pain or discomfort is associated with a change in frequency of bowel movements.

3. The beginning of pain or discomfort is associated with a change in the appearance or consistency (hardness or softness) or stools.

There are other symptoms that doctors use to support the diagnosis of IBS and to further divide it into three different categories. The three categories are determined by whether there is a predominant stool pattern of diarrhea or constipation or is the stool pattern alternating diarrhea and constipation. The supporting symptoms are as follows.

1. <3 bowel movements per day

2. >3 bowel movements per day (diarrhea)

3. Hard or lumpy stools

4. Loose, mushy or watery stools

5. Straining during a bowel movement

6. Urgency, or the sense that you need to rush to the bathroom to have a bowel movement

7. Feeling of incomplete emptying after a bowel movement

8. Passage of mucus or whitish material during a bowel movement

9. Feeling of abdominal fullness, bloating or swelling

Therefore, the diagnosis is made by a report of the symptoms and the doctor excluding other causes. The extent to which other conditions are excluded is highly variable and doctor dependent. Self-diagnosis of IBS should be avoided because serious conditions can cause symptoms that mimic IBS.

Theories of the cause of IBS are not proven. Serotonin, a chemical present in both the brain and the gut, has been suspected. An imbalance in serotonin has been blamed for IBS. Serotonin increases the contractions of the intestine. Several medications that either increase or decrease serotonin have been developed to treat constipation or diarrhea predominant IBS.

More recently, research has been focusing on the common report of many people with IBS of a distinct time that their IBS symptoms began, often after some type of intestinal infection such as food poisoning, traveler's diarrhea or gastroenteritis. This "post-infectious" theory has lead to theories of bowel injury and/or alterations in bacteria in the intestine. An imbalance of "good and bad" bacteria in the intestine is a theory. Some are treating people with antibiotics and/or probiotics. Antibiotics kill bacteria. Probiotics are live bacteria that are "good bacteria" like acidophilus and lactobacillus that can be taken as pill, capsule, powder or eaten or drank in yogurt or milk.

Food intolerances have been proposed as a cause of IBS by some, especially in Europe, but have not been accepted by most doctors in the U.S. Trials of elimination diets, with or without the use of food allergy or antibody tests have been reported in a few studies or a lot of testimonials to be helpful.

Lactose intolerance is a common condition that can cause symptoms that may be misdiagnosed as IBS and resolve with avoidance of lactose. Undiagnosed colitis or Crohn's disease can be a cause of symptoms that can be diagnosed by colonoscopy with biopsy of the intestine. Blood tests for colitis and Crohn's disease also now exist.

More recently, undiagnosed Celiac disease has emerged as a cause of what had been previously been diagnosed as IBS in as many of 20% of people. Those with a diagnosis of IBS should be screened for Celiac disease, as it is a common condition, affecting 1 in 100 people. The symptoms of abdominal pain, bloating, gas and diarrhea are common symptoms of Celiac disease and it is now known that untreated Celiac can be constipated. Gluten free diet relieves these symptoms in people who are gluten sensitive. Further information about irritable bowel syndrome, food intolerance, colitis, Crohn's disease, lactose intolerance and Celiac disease may be found at www.thefooddoc.com

If you have symptoms suggestive of IBS or have been diagnosed as having IBS it is important that you have an evaluation by a physician and other causes including colitis, Crohn's disease, lactose intolerance, and Celiac disease are excluded. Food intolerance should also be considered. Minimum evaluation should include a blood count, stool tests for blood and pus cells, screening lab tests for Celiac disease, colitis, Crohn's and a colonoscopy. Talk to your doctor about the diagnosis and how other causes can be or have been excluded before accepting the diagnosis of IBS.