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Irritable Bowel Syndrome (IBS)

Last updated May 5, 2018

Approved by: Krish Tangella MD, MBA, FCAP

Dr. Bob explains irritable bowel syndrome and how to treat it.


What are the other Names for this Condition? (Also known as/Synonyms)

  • Functional Bowel Disease
  • Irritable Colon Syndrome
  • Mucous Colitis

What is Irritable Bowel Syndrome? (Definition/Background Information)

  • Irritable Bowel Syndrome (IBS) is a gastrointestinal tract disorder that affects the large intestine, which is also known as the colon.
  • Normally, food that is consumed is pushed through the digestive tract by muscle contractions of the intestines. In individuals with IBS, contractions either last too long or too short a time. This creates problems in proper food movement through the digestive tract.
  • Common symptoms associated with IBS include abdominal pain, bloating, diarrhea, and constipation. In most cases, these symptoms do not become extreme and can be controlled through a combination of medications and lifestyle changes.

Irritable Bowel Syndrome is classified and diagnosed as four subtypes, depending on the individual’s stool consistency. The IBS classification is important, as it determines what medications and treatments the individual shall receive.

  • IBS with constipation: Hard stools at least 25% of the time, loose stools less than 25% of the time
  • IBS with diarrhea: Loose stools at least 25% of the time, hard stools less than 25% of the time
  • Mixed IBS: Hard stools at least 25% of the time, loose stools at least 25% of the time
  • Unsubtyped IBS: Hard stools less than 25% of the time, loose stools less than 25% of the time

Who gets Irritable Bowel Syndrome? (Age and Sex Distribution)

  • Irritable Bowel Syndrome is believed to affect anywhere between 3-20% of the population
  • IBS has been found to affect females twice as often as it affects males
  • While the disorder can occur at any age, it usually begins during young adulthood. Studies have found that in most cases, it occurs in individuals under the age of 45 years

What are the Risk Factors for Irritable Bowel Syndrome? (Predisposing Factors)

Common risk factors of Irritable Bowel Syndrome include:

  • Young age: Most cases of IBS occur in individuals under the age of 45 years
  • Gender: Females are twice as likely to suffer from the condition, as males
  • Family history: Individuals having relatives with IBS, are more likely to suffer from the syndrome themselves
  • Stress: Many cases of IBS arise due to stress
  • Low-fiber diet: Fiber is important in your diet, as it promotes the movement of food material through the digestive tract, increases the weight of your stools, and also softens your stools

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Irritable Bowel Syndrome? (Etiology)

Currently, researchers do not know the exact cause of Irritable Bowel Syndrome. A variety of factors are believed to contribute towards it, including:

  • Abnormal serotonin levels: Serotonin is a chemical messenger important in brain function and digestive system function; when abnormal levels are present, the digestive system cannot function properly
  • Improper diet: Many individuals have been found to suffer from IBS when their intake of food and drink, like chocolate, alcohol, dairy products, and carbonated drinks increase
  • Stress: While the physiological link between stress and IBS has not been established, research has determined that stress aggravates the symptoms further
  • Hormone imbalances: Studies have found that in women, IBS is more likely to occur during one’s menstrual period. Furthermore, postmenopausal women have been found to suffer from the condition, though with fewer symptoms than menstruating women. This suggests that reproductive hormones impact one’s likelihood of developing IBS
  • Genetics: Individuals with a family history of the disorder have an increased likelihood of developing it themselves. It is unclear whether this increased risk is due to genetic or environmental factors

Although the causes of Irritable Bowel Syndrome are unclear and varied, the physiology of the disorder is the same in all cases. In a healthy individual, the GI tract muscles contract in a coordinated manner to move food through the digestive system. In individuals with IBS, however, muscle contraction either occurs too quickly or too slowly, resulting in abnormal movement of food.

What are the Signs and Symptoms of Irritable Bowel Syndrome?

Common signs and symptoms of Irritable Bowel Syndrome include:

  • Abdominal pain, cramps
  • Bloating, passing gas
  • Diarrhea
  • Constipation
  • Mucous in stools
  • Abnormal bowel movements
  • Loose, watery stools or hard, lumpy stools (or alternating bouts of both)
  • Loss of appetite

While these signs may occur in many individuals after consuming a large meal, a diagnosis of IBS is made, if these signs and symptoms are present, at least three times a month over a three-month period.

How is Irritable Bowel Syndrome Diagnosed?

There are no formal tests to diagnose Irritable Bowel Syndrome. In most cases, the disorder is diagnosed based on one’s signs and symptoms. Due to the lack of formal tests, the Rome criteria for diagnosing IBS have been developed. According to this criteria:

  • Abdominal pain is present over a 12-week period (it does not have to be constant, or present during consecutive weeks)
  • Stool frequency or stool consistency has changed
  • Mucous is present in the stool
  • Straining, or a feeling that you cannot completely empty your bowels, occurs

Your physician may, however, conduct tests to rule out other medical problems, such as:

  • A blood test may be performed to check for an abnormal blood count
  • Stool cultures may be checked for infection
  • A colonoscopy may be conducted, if the symptoms arise after the age of 50 years
  • The physician may also suggest removing dairy products from your diet for a few weeks, to see if you are lactose intolerant. If symptoms improve, then it is likely that IBS may not be the problem

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Irritable Bowel Syndrome?

The possible complications from Irritable Bowel Syndrome could include:

  • While IBS does not cause any permanent damage to the digestive tract, it can impact one’s quality of life
  • Due to the signs and symptoms of the disorder, it is often difficult to engage in social activities or leave home for extended periods of time
  • It has also been found that the bowel disorder impacts one’s ability to attend work. Studies have found that individuals with IBS are three times more likely to take sick days, as those without IBS
  • IBS can also impact one’s ability to have a healthy sexual life. Symptoms of the disorder often make it difficult to get in the mood, or take part in sex

How is Irritable Bowel Syndrome Treated?

The symptoms of Irritable Bowel Syndrome can be treated using medications and by making lifestyle and dietary changes. A variety of medications can be used to treat IBS. These include:

  • Fiber supplements (Metamucil, Citrucel) - promote normal movement of food through the digestive tract and promote the formation of normal stools
  • Anti-diarrheal medications (Imodium) - to control diarrhea
  • Anticholinergic medications - to relieve painful bowel movements
  • Alosetron (Lotronex) is a medication that relaxes the colon and slows the movement of food through the lower bowel. It has only been approved for use by ‘females’
  • Lubiprostone (Amitiza) increases fluid secretion in the small intestine to promote stool movement. It is approved for use by men and women

Dietary changes that eliminate high-gas foods and increase fiber intake are suggested, to improve the symptoms associated with IBS. Increased water intake and regular exercise is also suggested, in order to improve symptoms.

How can Irritable Bowel Syndrome be Prevented?

  • Due to a lack of knowledge about the cause factors of Irritable Bowel Syndrome, it is difficult to prevent its occurrence
  • It is, however, important to reduce stress and eat a proper healthy diet in order to reduce your likelihood of developing IBS

What is the Prognosis of Irritable Bowel Syndrome? (Outcomes/Resolutions)

  • In most cases, Irritable Bowel Syndrome is a lifelong disorder. Although it does not cause any permanent damage to the colon, without proper treatment it will impact your lifestyle and ability to work
  • Through dietary changes and use of proper medications, the symptoms can be controlled and most individuals can undertake their normal activities

Additional and Relevant Useful Information for Irritable Bowel Syndrome:

The “Rome III Diagnostic Criteria for Functional Gastrointestinal Disorders” serves as a classification system for functional gastrointestinal disorders (FGIDs), such as Irritable Bowel Syndrome, functional dyspepsia (abdominal discomfort after eating), functional heartburn, and functional constipation.

What are some Useful Resources for Additional Information?


References and Information Sources used for the Article:


Helpful Peer-Reviewed Medical Articles:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Aug. 21, 2013
Last updated: May 5, 2018