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 endoscopy with biopsies and radiological testing to help confirm a diagnosis of Crohn's disease. You may have one or more of the following tests and procedures:
- 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 blood in your stool.
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- 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. Clusters of inflammatory cells called granulomas, if present, help confirm the diagnosis of Crohn's.
- 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. 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, which are transmitted to a computer you wear on your belt. The images are then downloaded, 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.
- 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.
- Small bowel imaging. This test looks at the part of the small bowel that can't be seen by colonoscopy. After you drink a liquid containing barium, doctors take X-ray, CT or MRI images of your small intestine.
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