Jay Yepuri, MD, MS, is board-certified in gastroenterology. He is a partner with Digestive Health Associates of Texas and a medical director at Texas Health Harris Methodist HEB Hospital.
Irritable bowel syndrome (IBS) is a functional gastrointestinal (GI) disorder. Symptoms include crampy abdominal pain, bloating, constipation, and/or diarrhea. The severity of symptoms varies from mildly annoying to debilitating.
In a person with IBS, the muscles in the colon (part of the large intestine) that move digested food along are exceptionally sensitive to certain stimuli or triggers. IBS is diagnosed based on symptoms (especially chronic abdominal pain and altered bowel habits) and an evaluation of the GI tract to rule out other diagnoses.
The causes of IBS aren’t well understood, and it’s often managed with a combination of diet and lifestyle modifications and medications. IBS is a chronic condition that can be controlled, but not cured.
The causes of IBS are complex and somewhat unknown. There may be an interplay between pain sensitivity, gut motility problems, low-grade inflammation, and gut bacteria and hormones dysfunction in brain and gut communication. IBS sometimes develops after an infection in your digestive tract or after trauma. It also tends to run in families, and research suggests that gene mutations play a role.
Doctors may recommend dietary (fiber, low-FODMAP diet) and other lifestyle changes (exercise, sleep) and therapies. There are also over-the-counter (OTC) and prescription medications that can be used to target symptoms of diarrhea, constipation, or pain. Therapies can include cognitive behavioral therapy, gut-directed hypnotherapy, and relaxation training.
IBS is a diagnosis of exclusion. Your doctor will run blood and fecal occult tests and ask about your family and personal medical history. After ruling out infections and other digestive diseases, you may be diagnosed with one of three types of IBS based on symptoms:
Eating smaller, more frequent meals and gradually increasing fiber, especially soluble fiber (nuts, beans, fruit), can help improve symptoms in IBS. Your doctor may suggest temporarily avoiding fatty foods and other common triggers or following a low-FODMAP diet, which eliminates hard-to-digest carbohydrates for six to eight weeks and then slowly reintroduces them.
Disorders of the gastrointestinal tract. Structural GI disorders are when the GI tract looks and functions abnormally. In functional GI disorders, such as IBS, the GI tract looks normal yet isn’t functioning properly.
A chronic inflammation of the gastrointestinal tract that can cause symptoms such as rectal bleeding, mucus in stools, abdominal pain, weight loss, and persistent diarrhea. Inflammatory bowel disease (IBD) is an umbrella term for three conditions: Crohn's disease, ulcerative colitis, and indeterminate colitis.
Iron deficiency anemia is a condition in which you lack adequate red blood cells to carry oxygen through your body due to low iron. Iron levels can be low due to inadequate dietary iron intake, nutrient malabsorption, or bleeding.
Tests that measure hydrogen and methane in the breath after a person drinks a sugar solution of either lactulose or glucose. Breath tests are a non-invasive way to diagnose or rule out small intestinal bacterial overgrowth (SIBO) in people with bloating or bowel problems and suspected IBS.
Malabsorption is when the small intestine does not absorb nutrients properly. Celiac disease, inflammatory bowel disease (IBD), and small intestinal bacterial overgrowth (SIBO) can lead to malabsorption and subsequent nutrient deficiencies and anemia. It is not believed that IBS results in the malabsorption of many key nutrients, yet some malabsorption issues may be behind IBS symptoms.
National Institute of Diabetes and Digestive and Kidney Diseases. Treatment for irritable bowel syndrome. Updated November 2017.
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Deloughery TG. Iron deficiency anemia. Med Clin North Am. 2017;101(2):319-332. doi:10.1016/j.mcna.2016.09.004
Salem A, Roland BC. Small intestinal bacterial overgrowth (SIBO). J Gastroint Dig Syst. 2014;4:225. doi:10.4172/2161-069X.1000225
Cleveland Clinic. Gastrointestinal disorders. Updated October 25, 2016.