The diagnosis of Irritable Bowel Syndrome relies on a diagnosis of exclusion. Because the symptoms of IBS share the symptoms of so many other intestinal illnesses, it sometimes takes years before a correct diagnosis is made to exclude the obvious, and not so obvious, conditions which present symptoms similiar to IBS.

Physicians rely on a variety of procedures and laboratory tests to confirm a diagnosis. The Rome II Criteria, however now defines markers which allows professionals to diagnose IBS after a careful examination of a sufferers medical history and physical abdominal examination which looks for any 'red flag' symptoms.

Commonly used medical tests can be categorized as follows:

1. Food/Nutrition/Malabsorption:

• Hydrogen breath test
• Lactose intolerance test
• Celiac disease exam
• GallBladder disease tests
  

  2. Stool examinations:

• Bristol Stool Form Scale
• Stool culture
• Stool C. difficile toxin
• Stool ova and parasites
  

  3. Radiological procedures:

• Abdominal CT Scan
• Abdominal MRI
• Abdominal Ultrasound
• Lower GI Series
• Upper GI Series
  

  4. Endoscopic procedures:

• Barium Enema
• Colonoscopy
• Sigmoidoscopy
• Upper Endoscopy