How Common is Irritable Bowel Syndrome (IBS) Really?

by Constance Pietrzak, M.D. Health Professional

Irritable bowel syndrome (IBS) is the most commonly diagnosed disorder of the gastrointestinal tract in the United States. It accounts for about 30 percent of all referrals to gastroenterologists, and this condition contributes significantly to health care costs. It used to be a diagnosis of exclusion where numerous medical tests needed to be completed with negative results in order to finally make the diagnosis. Over the years, it has been determined that patients with IBS tend to experience specific symptoms, which have been summed up in diagnostic criteria by the gastroenterology community.

As a result of using the Rome criteria, it is recommended that IBS be diagnosed according to symptom-based criteria. Using these criteria along with outlined “alarm symptoms” has helped minimize the use of diagnostic testing that could have the potential to unnecessarily place someone at risk for adverse risks or complications. The cause of IBS remains incompletely understood and is thought to be multifactorial, including alterations in gut motility, hypersensitivity of the gut, possible inflammation occurring in the gut lining, changes in the bacteria that reside in the gut (i.e. the microbiome), and possible overgrowth of bacteria in the gut.

How common is IBS and what are the symptoms?

As mentioned, IBS is very common. It affects 10 to 20 percent of the population. More females are affected than males by a ratio of about 1.5-3:1. The reason for so many more females presenting with IBS is unknown at this time. Some contributing factors to this difference include differences in health care-seeking behavior in men versus women and other psychosocial factors accounting for the health care-seeking behaviors.

The symptoms outlined in the Rome criteria include abdominal pain or discomfort, improvement in pain after having a bowel movement, and onset of pain with a change in stool form or change in stool frequency. Diagnosis is based on certain timing and frequency of symptoms and time of symptom onset. An important part of diagnosing IBS is ensuring that there are no “alarm symptoms.” These include unexplained weight loss, blood in the stool, fevers, anemia, and family history of colon cancer, inflammatory bowel disease, celiac or persistent/severe symptoms. Once a complete history and physical exam are completed, the number and type of diagnostic tests needed to diagnose IBS are based on guidelines developed by the gastroenterology societies.

Are you sure it’s IBS?

The symptoms of IBS are nonspecific and can mimic many different medical conditions or illnesses. Some of these conditions include constipation, food allergies or food sensitivities, celiac disease, inflammatory bowel disease (Crohn’s disease or ulcerative colitis), side effect of medications or drugs, lymphoma, other disorders of the small intestines causing malabsorption, abnormal gut motility, colon cancer, ovarian cancer, bowel obstruction, thyroid abnormalities or various neurologic disorders. It is important to note that not all of these disorders need to necessarily be “ruled out” before making a diagnosis of IBS any longer, as long as the established guidelines for diagnosis are appropriately followed. Studies have shown that once a diagnosis of IBS is made, only about 0.7 to 6.5 percent of people end up presenting with an organic cause for their symptoms later.

Over-diagnosed or not?

IBS is a real disorder of the gastrointestinal tract causing symptoms that affect quality of life and can even be debilitating. Management of IBS involves treating the symptoms (constipation, diarrhea, and abdominal pain), as well as psychological intervention given the strong association of IBS with psychological distress. Even though the numbers of patients diagnosed with IBS seem high, the true number may be even higher. Many people with mild symptoms may not seek medical care and attempt to treat their symptoms on their own. Others may not have access to health care, and, therefore, avoid evaluation for symptoms of intermittent periods of constipation or diarrhea. Others may not seek care for fear of finding an organic cause, such as cancer, if testing is required. As mentioned above, in most cases of symptoms common to IBS and other disorders, only about 1-6 percent of patients actually have another disease.

Everyone at some point has brief periods of alterations in their bowel habits (i.e. periods of constipation, diarrhea, with associated abdominal pain). If these occur with some sort of frequency, persistence, or for several months, you should talk to your doctor. Based on your symptoms and review for any alarm symptoms, IBS can be easily diagnosed and treated to help improve your quality of life.

Constance Pietrzak, M.D.
Meet Our Writer
Constance Pietrzak, M.D.

Constance Pietrzak, M.S., M.D., is a gastroenterologist with Advocate Medical Group in Chicago. Through her work with HealthCentral, she strives to expand knowledge on gastroesophageal reflux disease (GERD) and inflammatory bowel disease (IBD). Follow Constance on Twitter for timely updates on IBD, and more.