A diagnosis of IBS depends largely on a complete medical history and
physical exam. Your doctor may also recommend conducting several tests,
including stool studies to check for infection or malabsorption problems. He or
she may perform a flexible sigmoidoscopy — a test that examines the lower part
of the colon (sigmoid) with a flexible, lighted tube (sigmoidoscope).
In some cases, your doctor may perform a colonoscopy, a diagnostic test in
which a small, flexible tube is used to examine the entire length of the colon.
These tests help rule out more serious conditions such as ulcerative colitis,
Crohn's disease and colorectal cancer.
You may also have tests to determine whether you're lactose intolerant.
Lactase is an enzyme you need to digest the sugar found in dairy products. If
you lack this enzyme, you may have problems similar to those caused by IBS,
including abdominal pain, gas and diarrhea. To find out if this is the cause of
your symptoms, your doctor may order a breath test or ask you to exclude milk
and milk products from your diet for several weeks to see if a lactose
intolerance is causing your symptoms. Celiac disease (nontropical sprue) is a
sensitivity to wheat protein that may cause symptoms like IBS as well. Blood
tests may help rule out that disorder.
Because there are usually no physical signs of disease in IBS, diagnosis is
often a process of elimination. To help in this process, researchers have
developed diagnostic criteria, known as Rome
criteria, for IBS and other functional gastrointestinal disorders — conditions
in which the bowel appears normal but doesn't function normally.
According to these criteria, you must have certain signs and symptoms before
a doctor diagnoses IBS. The most important are abdominal pain, and diarrhea or
constipation lasting at least three months. You also need to have at least two
of the following, one-fourth or more of the time:
- A change in the frequency or
consistency of your stool. For example, you may change from having one
normal,
formed stool every day to three or more loose stools daily. Or you may have
only one hard stool every three to four days.
- Straining, urgency or a feeling
that you can't empty your bowels completely.
- Mucus in your stool.
- Bloating or abdominal distension.
