Tests and diagnosis

By Mayo Clinic Staff

Your doctor will likely diagnose Crohn's disease only after ruling out other possible causes for your signs and symptoms, including irritable bowel syndrome (IBS), diverticulitis and colon cancer. To help confirm a diagnosis of Crohn's disease, you may have one or more of the following tests and procedures:

  • Blood tests. Your doctor may suggest blood tests to check for anemia — a condition in which there aren't enough red blood cells to carry adequate oxygen to your tissues — or to check for signs of infection. Two tests that look for the presence of certain antibodies can sometimes help diagnose which type of inflammatory bowel disease you have, but not everyone with Crohn's disease has these antibodies. While your doctor may order these tests, a positive finding doesn't mean you have Crohn's disease and a negative finding doesn't mean that you're free of the disease. Because these tests aren't yet definitive, the American College of Gastroenterology doesn't currently recommend antibody or genetic testing for Crohn's disease.
  • Fecal occult blood test. You may need to provide a stool sample so that your doctor can test for blood in your stool.
  • Colonoscopy. This test allows your doctor to view your entire colon using a thin, flexible, lighted tube with an attached camera. During the procedure, your doctor can also take small samples of tissue (biopsy) for laboratory analysis, which may help confirm a diagnosis. Some people have clusters of inflammatory cells called granulomas, which help confirm the diagnosis of Crohn's disease because granulomas don't occur with ulcerative colitis. Risks of colonoscopy include perforation of the colon wall and bleeding.
  • Flexible sigmoidoscopy. In this procedure, your doctor uses a slender, flexible, lighted tube to examine the sigmoid, the last section of your colon.
  • Computerized tomography (CT). You may have a CT scan, a special X-ray technique that provides more detail than a standard X-ray does. This test looks at the entire bowel as well as at tissues outside the bowel that can't be seen with other tests. Your doctor may order this scan to better understand the location and extent of your disease or to check for complications such as partial blockages, abscesses or fistulas. Although not invasive, a CT scan exposes you to more radiation than a conventional X-ray does. CT enterography is a special CT scan that provides better images of the small bowel. This test has replaced barium X-rays in many medical centers.
  • Magnetic resonance imaging. An MRI scanner uses a magnetic field and radio waves to create detailed images of organs and tissues. Most MRI machines are large, tube-shaped magnets. During the test, you lie on a movable table inside the MRI machine. This test is very helpful in diagnosing and managing Crohn's disease. It's biggest advantage is that there is no radiation exposure. It's particularly useful for evaluating a fistula around the anal area (pelvic MRI) or the small intestine (MRI enterography).
  • Capsule endoscopy. If you have signs and symptoms that suggest Crohn's disease but other diagnostic tests are negative, your doctor may perform capsule endoscopy. For this test you swallow a capsule that has a camera in it. The camera takes pictures, which are transmitted to a computer that you wear on your belt. The images are then downloaded, displayed on a monitor and checked for signs of Crohn's disease. Once it's made the trip through your digestive system, the camera exits your body painlessly in your stool. Capsule endoscopy is generally very safe, but if you have a partial blockage in the bowel, there's a slight chance the capsule may become lodged in your intestine. In addition, the images provided by capsule endoscopy may not be detailed enough. Endoscopy with biopsy is often still needed to confirm the diagnosis of Crohn's disease and to exclude other causes of your symptoms.
  • Double balloon endoscopy. For this test, a longer scope is used to look further into the small bowel where standard endoscopes don't reach. This technique is useful when capsule endoscopy shows abnormalities, but the diagnosis is still in question. It allows for biopsy of the abnormal area. It's usually performed in specialized endoscopy centers.
  • Small bowel imaging. This test looks at the part of the small bowel that can't be seen by colonoscopy. After you drink a solution containing barium, X-ray, CT or MRI images are taken of your small intestine. The test can help locate areas of narrowing or inflammation in the small bowel that are seen in Crohn's disease. The test can also help your doctor determine which type of inflammatory bowel disease you have.
  • Barium enema. This diagnostic test allows your doctor to evaluate your large intestine with an X-ray. Before the test, you receive an enema with a contrast solution  containing barium. The barium dye coats the lining of the bowel, creating a silhouette of your rectum, colon and a portion of your small intestine that's visible on an X-ray. This test is rarely done anymore because of the availability of colonoscopy and CT scanning.
Aug. 09, 2011