There is no definitive diagnostic test for Crohn's disease. If you have Crohn's disease, your symptoms and the results of various tests will fit a pattern over time. This pattern will be best explained by Crohn's disease.
It may require months for your doctor to diagnose Crohn's disease with certainty.
Your doctor will look for evidence of intestinal inflammation. He or she will try to distinguish it from other causes of intestinal problems such as infection or ulcerative colitis. Ulcerative colitis is a related disease that also causes intestinal inflammation.
Test abnormalities that are often, but not always, found in people with Crohn's disease include:
Blood tests. Show a high white blood cell count or other signs of inflammation. They can also test for anemia, a reduced number of red blood cells.
Autoantibody tests. Reveal antibodies in the blood of people with Crohn's disease. They may help distinguish between inflammation caused by Crohn's disease versus ulcerative colitis.
Stool tests. Also called feces or bowel movement tests.
Detect small amounts of blood from irritated intestines.
Make sure that there is no infection causing the symptoms.
Upper gastrointestinal (GI) series. A test in which x-ray pictures are taken of your abdomen after you drink a barium solution that shows up on X-rays. As the liquid trickles down, it traces the outline of your intestines on the X-ray. An upper GI series can reveal places in the small intestine that are narrowed. It also can highlight ulcers and fistulas. These abnormalities are found more often in Crohn's disease than in ulcerative colitis, or other conditions that cause symptoms similar to Crohn's disease symptom.
Flexible sigmoidoscopy or colonoscopy tests. These tests use a small tube with an attached camera and light. The tube is inserted into your rectum, allowing your doctor to view the insides of your large intestine. These tests are usually done when Crohn's disease is suspected.
MR Enterography. A relatively new test that provides pictures of the entire intestine without radiation. It uses magnetic resonance imaging to show areas of Crohn's involvement.
Wireless capsule endoscopy. The test involves swallowing a pill-sized object that is a tiny little video camera. It sends pictures of your small intestine wirelessly. Unlike x-ray studies such as the upper GI series, no x-ray radiation is involved.
Biopsy. The removal of a small sample of tissue from the lining of the intestine. The material is examined in a laboratory for signs of inflammation. A biopsy is most helpful to confirm Crohn's disease and to exclude other conditions.