Causes and Diagnoses

Causes and Diagnoses of Irritable Bowel Syndrome

Researchers have not identified a single cause of irritable bowel syndrome. In fact, there may be many causes, with each patient affected by a different set of conditions.

Common causes include:

  • Stress: Stress can cause your colon to spasm or move uncontrollably.
  • Food triggers: Food sensitivities are highly individualized, but the most common ones are spicy foods, fatty foods, cruciferous vegetables, onions, and beans.
  • Gastroenteritis: This is called post-infectious IBS.
  • Heredity: Many patients report that family members have similar symptoms.

Nowadays, it is fairly well established that braingut dysregulation plays a critical role in the onset and maintenance of IBS. Further, in an effort to control their symptoms, patients with IBS and other functional bowel disorders often engage in behaviors that actually make symptoms worse.

Diagnosing Irritable Bowel Syndrome

Diagnosing irritable bowel syndrome begins with a physical exam and health history. Tests may include:

  • Blood test: Lab tests can determine if you have an infection or other illness that causes inflammation.
  • Stool sample: This lab test checks for abnormal bacteria and parasites in your digestive tract.
  • Breath test: This test can identify the presence of excessive bacteria that can cause IBS.
  • X-rays: X-ray images can indicate the location and severity of a blockage or infection.
  • Ultrasound: Ultrasound testing uses reflected sound waves to create images of the inside of your body. Unlike an X-ray or CT scan, there is no ionizing radiation exposure.
  • Upper endoscopy: An endoscope (a thin, lighted tube with a camera attached to it) is passed through your mouth and esophagus to your stomach and duodenum. Your physician can look at pictures of your digestive tract and evaluate any abnormalities or blockages.
  • Lower GI (barium enema): A series of X-rays are taken after you have received an enema containing barium, a contrast material that coats your colon and shows up well on X-rays.
  • Colonoscopy: An endoscope (long, flexible tube) with a lighted camera goes through the colon, allowing your physician to view the lining. A sigmoidoscopy uses the same technology but examines only the sigmoid colon (the lower third).
  • Virtual colonoscopy: A CT scan can be used in conjunction with air and contrast dye to perform a virtual colonoscopy.
Legal Information

By clicking on these websites, you are leaving the Northwestern Medicine website. These websites are independent resources. Northwestern Medicine does not operate or control the content of these websites. By visiting these websites, you agree to this third party’s terms of use for their website.