How is IBS diagnosed?
The starting point of the diagnosis is a detailed history to identify the characteristic symptoms of IBS and a physical examination.
Laboratory blood and stool tests, x-rays, and endoscopic procedures (e.g., colonoscopy) are used not to make the diagnosis but to rule out other diseases of the bowel, which can present with similar symptoms. These tests are usually normal in patients with IBS.
The first step in making a positive diagnosis of irritable bowel syndrome (IBS) is for the doctor or other health care provider to identify if an individual has the symptoms of IBS.
This is best determined by the use of the Rome Criteria, which is a collection of the most common symptoms that typify the disorder.
This includes abdominal pain or discomfort for several months that is associated with two of the following:
- the pain or discomfort is relieved by defecation,
- the pain or discomfort is associated with an increase or decrease in stool frequency, and/or
- the pain or discomfort is associated with the stools becoming harder or softer in consistency.
The next important step is to look for signs and symptoms that are suggestive of a condition other than IBS, such as inflammatory bowel disease or celiac disease. These signs and symptoms have been referred to as “alarm signs” or “red flags.”
- anemia and other abnormal blood tests
- blood in the stool
- unexplained weight loss
- new onset of symptoms at the age of 50 or older
- family history of inflammatory bowel disease, colon cancer, or celiac disease
These alarm signs are usually not explained by IBS and can represent other medical problems. When these symptoms and signs occur, they should be brought immediately to the attention of a doctor who may perform additional tests.