A physician may be able to diagnose irritable bowel syndrome (IBS) based on a medical history and physical examination. A medical history can include questions about the duration and severity of symptoms, changes in bowel functioning and the relation of symptoms to bowel functioning.

Many of these questions may be embarrassing for children, as they are likely to focus on subjects such as gas and diarrhea. Parents are urged to explain to their children ahead of time that these questions are likely, and to help them understand that the information is necessary for the physician and should not cause shame.

Diet, current medications, activity and stress levels may also be discussed. To further pinpoint the source of symptoms, a physician may ask a parent to keep a food diary that lists all of the foods a child eats and any symptoms that accompany those meals. Or, a child may be asked to keep a record of times when they feel particularly stressed. This can be matched with the child’s symptoms to see if there is any correlation between these times of stress and symptom flare-ups.

A physical examination can identify signs of other illness that may be causing the symptoms. Such illnesses may include lactose intolerance, infection, diverticulosis, thyroid disorders, inflammatory bowel diseases (e.g., Crohn's disease or ulcerative colitis) or cancer. Tests used to rule out other causes of symptoms in children with IBS include blood tests, fecal tests, lactose intolerance tests (e.g., a breath test or the systematic elimination of dairy products from the diet), barium enema x-ray, endoscopy and others.

Children may be diagnosed with IBS if the examination shows no signs of intestinal disease or damage related to the symptoms. These children must have experienced abdominal pain or discomfort for at least 12 weeks (not necessarily consecutive) in the past year. In addition, children must meet at least two of the following criteria for a diagnosis of IBS:

• Pain is relieved with the passage of stool
• Change in frequency of bowel movements when pain begins
• Change in appearance of stool when pain begins