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What Is IBS?

Irritable bowel syndrome (IBS) is defined as abdominal discomfort or pain associated with changes in bowel habits that occur at least three days per month during the previous three months.1,2 Changes in bowel habits may include symptoms related predominantly to either diarrhea or constipation, but may also include a mixed sensation that alternates between diarrhea and constipation.2 IBS is unlikely to increase the risk for the development of cancer or inflammatory bowel disease.3 The estimated prevalence of IBS in North America ranges from 10% to 15% and mainly occurs in adolescents and adults.3 However, IBS is under-recognized and many patients with IBS symptoms do not consult a physician and are not formally diagnosed.3

What Are the Types of IBS?

There are three main types of IBS.3 The types of IBS may be characterized by the predominant stool pattern.

  1. IBS with constipation (IBS-C): Stools are typically hard or lumpy with the occasional loose or watery stool.
  2. IBS with diarrhea (IBS-D): Stools are typically loose or watery with the occasional hard or lumpy stool.
  3. Mixed IBS (IBS-M): IBS with alternating constipation and diarrhea. Bowel movements may alternate between hard or lumpy stools and loose or water stools.

What Causes IBS?

The exact cause of IBS is still not completely understood.4 To date, IBS is believed to be caused by multiple factors, including psychosocial, environmental, and gut physiology, which may work together to produce symptoms.5

  • Environmental factors may include having a genetic predisposition to abnormalities in the gut’s bacteria, diet, and infections.5,6
  • Gut physiology may change and is particularly important because issues such as inflammation, the movement of food and waste through the gut, and the way the body responds to disturbances in the gut may contribute to the development of IBS. 5,6
  • Psychosocial factors may include stress and psychologic disorders.5,6

These and other factors ultimately affect how the GI tract functions, causing symptoms of IBS.6

Symptoms of IBS

People with IBS usually complain of recurrent episodes of abdominal pain accompanied by changes in bowel habits, such as constipation, diarrhea, or alternating occurrences of constipation and diarrhea. Abdominal pain is commonly described as a cramping sensation, which at times may be severe. Having a bowel movement may relieve some of the abdominal pain.2

Other gastrointestinal symptoms of IBS may include:2

  • Feeling a lump in the throat
  • Belching
  • Acid reflux
  • Difficulty swallowing (dysphagia)
  • Feeling full soon after eating
  • Intermittent indigestion (dyspepsia)
  • Nausea
  • Chest pain not associated with heart disease
  • Abdominal bloating and flatulence or gassiness.

How is IBS Diagnosed?

IBS is defined by symptoms. For the diagnosis of IBS, gastroenterologists typically use the definition provided by the American College of Gastroenterology, which simply states IBS as abdominal pain with disordered bowel movements. However, this definition still has not yet been validated.6

There is currently no gold standard diagnostic method for IBS. Instead, there are several sets of symptom-based guidelines that may be used to correctly diagnose IBS. The detailed guidelines are the Manning criteria and the Rome III criteria. The Rome III criteria are not commonly used in clinical practice but are frequently used in research studies.6

To diagnose IBS, doctors may start with a physical examination and questions about medical history, particularly if there is a consistent history of symptoms characteristic of IBS. The next step may be laboratory tests, even though laboratory and invasive testing are minimized. Some laboratory tests routinely ordered may include a complete blood count, erythrocyte sedimentation rate test, and fecal occult blood tests.5 Sometimes symptoms may be mistakenly diagnosed as IBS when they can actually be signs of other diseases or disorders, such as celiac disease, inflammatory bowel disease, or colorectal cancer.2

How is IBS Treated and Managed?

Given that there is no cure, the goal of IBS treatment is to improve gastrointestinal symptoms and quality of life. The initial management strategy may be determined based on symptom severity and dominant symptom. There are several therapeutic approaches to managing IBS.5

  • Diet
  • Exercise
  • Stress management
  • Probiotics
  • Fiber supplements and laxatives
  • Medications
  • Alternative or complementary medicine
Written by: Truc Thanh | Last reviewed: June 2016.
  1. Ford AC, Moayyedi P, Lacy BE, et al; Task Force on the Management of Functional Bowel Disorders. American College of Gastroenterology monograph on the management of irritable bowel syndrome and chronic idiopathic constipation. Am J Gastroenterol. 2014;109 Suppl 1:S2-26; quiz S27.
  2. Wilkins T, Pepitone C, Alex B, Schade RR. Diagnosis and management of IBS in adults. Am Fam Physician. 2012;86:419-426.
  3. World Gastroenterology Organisation Global Guidelines. Irritable Bowel Syndrome: a Global Perspective. Accessed 1/7/16 at:
  4. Camilleri M, Lasch K, Zhou W. Irritable bowel syndrome: methods, mechanisms, and pathophysiology. The confluence of increased permeability, inflammation, and pain in irritable bowel syndrome. Am J Physiol Gastrointest Liver Physiol. 2012;303:G775-G785.
  5. Sayuk GS, Gyawali CP. Irritable bowel syndrome: modern concepts and management options. Am J Med. 2015;128:817-827.
  6. Lacy BE, Chey WD, Lembo AJ. New and emerging treatment options for irritable bowel syndrome. Gastroenterol Hepatol (N Y). 2015;11(4 Suppl 2):1-19.