How is IBS diagnosed?

There is no test that will tell your doctor whether you have irritable bowel syndrome (IBS). Instead, your doctor will make a diagnosis based on whether you have certain signs or symptoms. These signs and symptoms are called diagnostic criteria. For IBS, the most commonly used diagnostic criteria are called the Rome criteria.

Do my symptoms meet the Rome criteria?

Your doctor will tell you whether your symptoms suggest IBS. Before you meet with your doctor, keep a record of your symptoms and when they occur. Share the record with your doctor to help him or her determine whether your symptoms fit the criteria for IBS. The Rome criteria put emphasis on the pattern and onset of pain or discomfort, and then define subtypes based on whether constipation, diarrhea, or both are present.

In order for your doctor to diagnose IBS, according to the Rome criteria, you must have had:

• Abdominal pain or discomfort at least 3 days per month for the past 3 months.

You must also have had at least 2 of the following:

• Pain or discomfort that goes away after a bowel movement
• Pain or discomfort that began when the consistency (appearance) of your stool changed; for example, you went from having normal stool to having loose or dry stool
• Pain or discomfort that began when the frequency of your bowel movements changed; for example, you went from having 1 bowel movement every day to having 3 every day, or to only having 1 every few days.

What are the different subtypes of IBS?

IBS symptoms are different for each person. If you meet the Rome criteria, your doctor may use your symptoms to further classify your IBS as one of the 4 following subtypes:

• IBS with constipation (IBS-C)

o    hard or lumpy stools at least 25% of the time

o    loose or watery stools less than 25% of the time

• IBS with diarrhea (IBS-D)

o    loose or watery stools at least 25% of the time

o    hard or lumpy stools less than 25% of the time

• Mixed IBS (IBS-M)

o    hard or lumpy stools at least 25% of the time

o    loose or watery stools at least 25% of the time

• Unsubtyped IBS (IBS-U)

o   hard or lumpy stools less than 25% of the time

o   loose or watery stools less than 25% of the time

These subtypes help your doctor determine what treatments are most likely to help relieve your symptoms.