Diagnosis

Your doctor will likely diagnose Crohn's disease only after ruling out other possible causes for your signs and symptoms. There is no one test to diagnose Crohn's disease.

Your doctor will likely use a combination of tests to help confirm a diagnosis of Crohn's disease, including:

Blood tests

  • Tests for anemia or infection. 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. Expert guidelines do not 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 hidden (occult) blood in your stool.

Procedures

  • Colonoscopy. This test allows your doctor to view your entire colon and the very end of your ileum (terminal ileum) 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. Clusters of inflammatory cells called granulomas, if present, help confirm the diagnosis of Crohn's.
  • 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. 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 (MRI). An MRI scanner uses a magnetic field and radio waves to create detailed images of organs and tissues. MRI is particularly useful for evaluating a fistula around the anal area (pelvic MRI) or the small intestine (MR enterography).
  • Capsule endoscopy. For this test, you swallow a capsule that has a camera in it. The camera takes pictures of your small intestine, which are transmitted to a recorder you wear on your belt. The images are then downloaded to a computer, displayed on a monitor and checked for signs of Crohn's disease. The camera exits your body painlessly in your stool. You may still need endoscopy with biopsy to confirm the diagnosis of Crohn's disease.
  • Balloon-assisted enteroscopy. For this test, a scope is used in conjunction with a device called an overtube. This enables the doctor 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.