Irritable Bowel Syndrome (IBS)
Irritable bowel syndrome is a functional gastrointestinal disorder of the lower digestive tract in which the normal rhythmic movement of the gut (bowel) is disturbed, so the bowel doesn't work as it should. You may have trouble going to the toilet (constipation), or have very loose and urgent bowel motions or stools (diarrhoea). It is very common condition, up to one in 3 people will have IBS symptoms at some time in their life.
IBS is not a disease. It is a functional disorder with the absence of structural or biochemical abnormalities to explain the symptoms. IBS sometimes is called as "Spastic colitis," "irritable colon," and "nervous stomach".
People with IBS have colons that are more sensitive and reactive to things that might not bother other people, such as stress, large meals, gas, medicines, caffeine, or alcohol. With IBS, the nerves and muscles in the bowel are extra-sensitive.
Irritable bowel syndrome may be a big nuisance, but harmless. Although the syndrome can cause considerable pain and discomfort, it does not damage the digestive tract as diseases do. Also, irritable bowel syndrome does not lead to more serious digestive diseases later.
Irritable bowel syndrome is characterized by a group of symptoms in which abdominal pain or discomfort is associated with a change in bowel pattern, such as loose or more frequent bowel movements, diarrhea, or constipation. The symptoms include:
The abdominal pain or discomfort has two of the following three features:
Bleeding, fever, weight loss, nocturnal diarrhea, and persistent severe pain are not symptoms of IBS and may indicate other problems such as inflammation.
So far, the causes of IBS remain a mystery. Researchers have yet to discover any specific cause for IBS. The disease tends to strike almost exclusively among adults, and it is more common among women than men.
One theory is that people who suffer from IBS have a colon (large bowel) that is particularly sensitive and reactive to certain foods and stress. The immune system, which fights infection, may also be involved.
Recent research has reported that serotonin is linked with normal gastrointestinal functioning. Serotonin is a neurotransmitter, or chemical, that delivers messages from one part of the body to another. 95% of the serotonin in the body is located in the GI tract, and the other 5% is found in the brain. Cells that line the inside of the bowel work as transporters and carry the serotonin out of the GI tract. People with IBS, however, have diminished receptor activity, causing abnormal levels of serotonin to exist in the GI tract. As a result, people with IBS experience problems with bowel movement, motility, and sensation - having more sensitive pain receptors in their GI tract.
Other theory is that IBS is a result of inadequate fibre in modern diets. Over the years, our colons evolved to handle a large amount of fibre. In the past 100 years fibre has been reduced in our diets through the processing of foods. This lack of fibre causes irregular contractions of the large intestines. The symptoms will get worse if you eat poorly. Periods of stress seem to worsen the symptoms.
IBS also tends to occur with other pain disorders, such as fibromyalgia (49% of people also have IBS), chronic fatigue syndrome (51%), chronic pelvic pain (50%), and temporomandibular joint dysfunction (64%) (Whitehead WE et al 2002).
IBS flare-ups can be triggered by a number of factors, including allergies, diet, and stress:
Irritable Bowel Syndrome is diagnosed by its symptoms and by the absence of other diseases. If there is uncertainty about whether you have a more serious problem (e.g. if you have bleeding from the bowel, which does not occur in IBS) your doctor may order other tests such as a stool sample test, a sigmoidoscopy (to look at the lining of the last part of your bowel through a lighted tube), colonoscopy (to look at the lining of your large intestine through a flexible lighted tube) or a barium enema (to view the lining of your bowel on X-ray). If you have IBS, the results of all these tests are likely to be normal.
There is no test that can diagnose IBS. And, because the symptoms of IBS occur with so many diseases, a long list of conditions must be ruled out before IBS can be diagnosed.
Rome III Diagnostic Criteria for Irritable Bowel Syndrome 
Recurrent abdominal pain or discomfort at least 3 days per month in the last 3 months associated with 2 or more of the following:
The Rome III criteria are reliable only when there is no intestinal abnormality or abnormality in the metabolic process that would explain the symptoms.