Irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common disorder that affects the large intestine (colon).  Even though signs and symptoms are uncomfortable, IBS doesn't cause changes in bowel tissue or increase your risk of colorectal cancer.

The signs and symptoms of irritable bowel syndrome can vary widely from person to person and often resemble those of other diseases. Among the most common are:

  • Abdominal pain or cramping
  • A bloated feeling
  • Gas
  • Diarrhea or constipation — sometimes alternating bouts of constipation and diarrhea
  • Mucus in the stoo

To meet the definition of IBS, symptoms must occur at least three times a month. For most people, IBS is a chronic condition, although there will likely be times when the signs and symptoms are worse and times when they improve or even disappear completely. Only a small number of people with irritable bowel syndrome have severe signs and symptoms. Some people can control their symptoms by managing diet, lifestyle and stress. Others will need medication and counseling.

What causes IBS?

IBS results from a combination of several factors that can affect gastrointestinal (GI) functioning. This includes poor regulation of the muscle contractions of the GI tract, causing abnormal movement (referred to as dysmotility), increased sensitivity of the nerves attached to the intestinal tract that produce the electrical activity (called visceral hypersensitivity), or problems in the communication between the nerves of the brain and gut (known as brain-gut dysfunction). Any or all of these factors lead to the symptoms that we can recognize as IBS. Researchers believe a combination of physical and mental health problems (such as depression and anxiety disorders) can lead to IBS.


  • Many people report that their symptoms occur following a meal. Eating causes contractions of the colon. Normally, this response may cause an urge to have a bowel movement within 30 to 60 minutes after a meal. In people with IBS, the urge may come sooner and may be associated with pain, cramps and diarrhea. Certain foods may trigger spasms in some people. Sometimes the spasm delays the passage of stool, leading to constipation.
  • Certain food substances, like complex carbohydrates and caffeine, fatty foods, or alcoholic drinks, can cause loose stools in many people, but are more likely to affect those with IBS.
  • Researchers have found that women with IBS may have more symptoms during their menstrual periods, suggesting that reproductive hormones can increase IBS symptoms.
  • Emotional distress, like preparing for a speech, taking an examination or traveling, can produce intestinal symptoms of diarrhea, constipation or pain in everyone, but more so in those with IBS who seem more sensitive to these events.


To diagnose IBS, a health care provider will conduct a physical exam and take a complete medical history. The medical history will include questions about symptoms, family history of GI disorders, recent infections, medications, and stressful events related to the onset of symptoms.  Though IBS does not have a cure, the symptoms can be treated with a combination of:

  • Changes in the diet and nutrition
  • Medications
  • Probiotics
  • Therapies for mental health problems


It is important to see your doctor if you have a persistent change in bowel habits or if you have any other signs or symptoms of IBS because these may indicate a more serious condition, such as colon cancer.

Symptoms that may indicate a more serious condition include:

  • Rectal bleeding
  • Abdominal pain that progresses or occurs at night
  • Weight loss

Your doctor may be able to help you find ways to relieve symptoms as well as rule out colon conditions, such as inflammatory bowel disease and colon cancer. Your doctor can also help you avoid possible complications from problems such as chronic diarrhea.



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