Irritable Bowel Syndrome (IBS) is a common functional bowel disorder affecting the large intestine. Typical symptoms include abdominal pain, cramping, bloating, gas, and constipation or diarrhoea, or both.

The prevalence of functional bowel disorders is up to 40% and IBS is reported to be around 10% and the prevalence is quite similar across different countries, despite substantial lifestyle differences.

IBS doesn’t increase the risk for severe disease like colorectal cancer but it is a chronic disease with strong negative impact on daily life for many affected people around the globe.


IBS usually causes long-term symptoms of abdominal recurrent pain or discomfort associated with a change in frequency of stool and/or a change in form (diarrhoea/constipation) of stool.

Other typical symptoms are bloating, distension, flatulence and borborygmi. IBS is also often associated with other noncolonic complaints like dyspepsia, nausea and heartburn.

The symptoms may occur in episodes and strongly interfere with daily life and social functioning. Many IBS-patients experience worse times followed by times when symptoms improve or even disappear.

Symptoms are also usually associated with food intake and defecation.

You should always see a doctor if you experience persistent change in bowel habits or other signs or symptoms that can indicate a more serious condition.


Signs and symptoms that require immediate attention are:

  • Persistent pain (Not relieved by passing gas or a bowel movement)
  • Unintended weight loss
  • Bleeding – rectal bleeding,
  • Iron deficiency anemia
  • Diarrhea at night
  • Vomiting (unexplained)

Always consult a doctor if you have any questions regarding your symptoms.

Abdominal pain and cramping are typical symptoms of IBS. The pain is usually relieved by passing a bowel movement.

Bloating or feeling bloated is also typical for many IBS patients. Bloatings is also usually relieved by passing a bowel movement.

Flatulence or escess gas is usually reported as a symptom from IBS patients. The amount of gas is usually similar to people not affected by IBS but the gas causes symptoms for IBS patients.

Some patients experience periods of diarrhoea (IBS-D) while it sometimes alternates with periods of constipation (IBS-M).

Some IBS-patients experience periods of constipation (IBS-C) while others experience periods of alternating constipation/diarrhoea (IBS-M).


IBS can  be subtyped based on stool characteristics. IBS with diarrhoea (IBS-D), IBS with constipation (IBS-C) and IBS with mixed bowel habits or cyclic pattern (IBS-M).

Predominant bowel habits are based on stool form on days with at least one abnormal bowel movement.

IBS-patients commonly transition between these subtypes and other sub-classifications have been suggested.

Other suggested subclassifications are

  • IBS with predominant bowel dysfunction
  • IBS with predominant pain
  • IBS with predominant bloating
  • post infectious (PI-IBS)
  • food-induced (meal-induced)
  • stress-related IBS

Post infectious (PI-IBS) is today quite well characterized. We know for sure that IBS can develop after severe  diarrhoea (gastroenteritis) caused by bacteria or  virus.

> 25% of bowel movements with BSFS 1 or 2 and <25% of bowel movements with BSFS 6 or 7.

Alternative for epidemiology or clinical practice: Patient reports that abnormal bowel movements are usually constipation (like type 1 or 2 in BSFS).

>25% of bowel movements with BSFS 6 or 7 and <25% of bowel movements with BSFS 1 or 2.

Alternative for epidemiology or clinical practice: Patient reports that abnormal bowel movements are usually diarrhoea (like type 6 or 7 in BSFS).

>25% of bowel movements with BSFS 1 or 2 and >25% of bowel movements with BSFS 6 or 7.

Alternative for epidemiology or clinical practice: Patient reports that abnormal bowel movements are usually both constipation and diarrhoea (more than one-fourth of all the abnormal bowel movements were constipation and more than one-fourth were diarrhoea, using BSFS.

Patients who meet diagnostic criteria for IBS but whose bowel habits cannot be accurately categorized into 1 of the 3 groups above should be categorized as having IBS unclassified.



A subgroup of IBS patients has symptoms that...


IBS is a disease with widely accepted, well defined and objective criteria for diagnosis.

It is defined as a relapsing functional bowel disorder by symptom-based diagnostic criteria, in the absence of detectable organic causes.

The symptoms are not specific for IBS, as such symptoms may be experienced occasionally by almost every individual. To distinguish IBS from transient gut symptoms, experts have underscored the chronic and relapsing nature of IBS.

The most recent criteria for diagnosis of FGID, Bowel disorders like IBS was released during 2016 (Rome IV).

Rome IV criteria defines IBS as:

Recurrent abdominal pain, on average, at least 1 day per week in the last 3 months, associated with 2 or more of the following criteria:

1. Related to defecation

2. Associated with a change in frequency of stool

3. Associated with a change in form (appearance) of stool

Criteria fulfilled for the last 3 months with symptom onset at least 6 months before diagnosis.

The Rome Foundation

The Rome Foundation

The Rome Foundation is an independent organization (not-for-profit)  supporting activities related to the diagnosis and treatment of functional...

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The precise cause of IBS is unknown. Research have suggested a couple of possible explanations to why some people get IBS.


  • Research has indicated that the microflora i.e the bacteria in the gut differs between healthy and people with IBS. Our microflora has a key role in health and changes in intestinal bacteria could be invloved in IBS.
  • A surplus of bacteria in the intestines (bacterial overgrowth) has also been suggested as a possible cause.


  • As mentioned gastroenteritis , inflammation of the intestines caused by bacteria or virus, can lead to IBS.  However some IBS patients also have an increased number of immune-system cells in their intestines, even without previous gastroenteritis. There seems to be an immune response in IBS that is associated with at least pain and diarrhea.
  • The smooth muscles in the walls of the intestines normally move food we eat through the digestive tract. If the muscle movements are disturbed slower/faster IBS like symptoms can develop – gas, bloating, diarrhea, constipation. Dysfunction of the intestinal muscles could be involved in IBS.
  • The “gutbrain” (the enteric nervous system) and how it communicates with our brain has also been suggested to be involved in IBS. Disturbed function of this complicted nervous system could lead to greater than normal exoerience from normal bowel movement in IBS patients.


IBS triggers

IBS triggers

Irritable Bowel Syndrome (IBS) symptoms can be triggered by a variety of factors including for...

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Blomquist L Osterberg E, Krakau I, et al. A population study on irritable bowel syndrome and mental health. Scand J Gastroenterol. 2000.

F. Mearin, B. E. Lacy, L. Chang, W. D. Chey, A. J. Lembo, M. Simren, et al. Bowel Disorders. Gastroenterology. 2016.

ICD 10. ICD 10

P. et al. (MARCH 2016) Enck. Supplementary information S1 IBS Nat Rev Dis Primers. Nature Reviews. 2016.

P. Enck, Q. Aziz, G. Barbara, A. D. Farmer, S. Fukudo, E. A. Mayer, et al. Irritable bowel syndrome. Nat Rev Dis Primers. 2016;2:16014.

R. Spiller, Q. Aziz, F. Creed, A. Emmanuel, L. Houghton, P. Hungin, et al. Guidelines on the irritable bowel syndrome: mechanisms and practical management. Gut. 2007;56(12):1770-98.

S. A. Walter, L. Kjellstrom, H. Nyhlin, N. J. Talley and L. Agreus. Assessment of normal bowel habits in the general adult population: the Popcol study. Scand J Gastroenterol. 2010;45(5):556-66.

The Rome Foundation. Appendix A Rome III Diagnostic Criteria for Functional Gastrointestinal Disorders