IBS is called a functional disease, because it is a problem of the working of the gut, rather than being caused by the biology of the gut (which is known as organic disease). Of course, as time passes, the gut does become damaged, so there is these days some controversy about the distinction between a functional and an organic disease.

IBS is a syndrome because there are a wide range of symptoms (or a cluster of symptoms) including back pain and chest pain, as well as the more understandable bloating, constipation etc. And not everyone has all the possible symptoms.

This makes diagnosis quite tricky. It involves excluding any organic disease, and then checking to see if the characteristic symptoms are presenting. If diagnosis is not properly conducted, you can end up with painful, unnecessary and possibly damaging internal examinations.

These are the symptoms normally considered to be symptomatic of IBS. They are called the Rome II criteria.

At least 12 weeks, which need not be consecutive, in the

preceding 12 months of abdominal discomfort or pain that

has two of three features:

Relieved with defecation

and/or

Onset associated with a change in frequency of stool

and/or

Onset associated with a change in form (appearance) of stool

Supportive symptoms:

Fewer than three bowel movements per week

More than three bowel movements per day

Hard or lumpy stools

Loose (mushy) stools

Straining during a bowel movement

Urgency

Feeling of incomplete bowel movement

Passing mucus during a bowel movement

Abdominal fullness, bloating or swelling