Because there are no specific tests for irritable bowel syndrome (IBS), the illness must be diagnosed based on symptoms and by process of elimination, sometimes with the use of tests for other conditions.
The doctor takes a complete medical history, including a careful description of your symptoms. A physical exam and some routine laboratory tests are likely to be part of the exam, and a stool sample is useful for evidence of bleeding. The doctor will also ask whether your symptoms started after an episode of gastroenteritis, or if they seem to be triggered by specific foods or medications, particularly milk products (to rule out lactose intolerance) and foods and beverages that contain fructose or sorbitol. You may need to keep a food diary for a few weeks to help identify foods that provoke symptoms.
It's especially important to consider emotional and psychological triggers. The doctor will want to know what prompted the visit and will ask about your lifestyle and stress level. It's not unusual for a traumatic life event such as divorce or the loss of a job to wreak havoc on the bowels and the psyche.
Other symptoms that accompany the pain may offer clues. If there is pain in the lower abdomen and a change in bowel movements, an abnormality in the large intestine may be present. A combination of abdominal pain and fever can signal inflammation (for example, diverticulitis), which requires immediate medical attention.
Another major diagnostic clue is bleeding from the digestive tract. People with IBS can have rectal bleeding, but IBS does not cause bleeding. Instead, bleeding reflects another cause, such as hemorrhoids. Bright red blood generally comes from the lower digestive tract, while black, tarry blood generally comes from the upper gastrointestinal (GI) tract. If there is bleeding, more tests must be performed to determine the cause.
During the physical exam, the physician will look for tenderness in the abdomen. If the tenderness is located in the lower right part, it may signal ileitis or appendicitis, and in the upper right part, gallstones and inflammation of the gallbladder. The doctor will also check for a mass, which might be a tumor, a large cyst, or impacted stool. If the patient has IBS, the physical exam will usually not reveal anything other than perhaps a mildly tender abdomen. And lab tests are generally normal in IBS patients.
More Answers from Lawrence Friedman