How is Crohn's disease diagnosed?

A thorough physical exam and a series of tests may be required to diagnose Crohn's disease.

Blood tests may be done to check for anemia, which could indicate bleeding in the intestines. Blood tests may also uncover a high white blood cell count, which is a sign of inflammation somewhere in the body. By testing a stool sample, the doctor can tell if there is bleeding or infection in the intestines.

The doctor may do an upper GI series to look at the small intestine. For this test, the person drinks barium, a chalky solution that coats the lining of the small intestine, before x rays are taken. The barium shows up white on x-ray film, revealing inflammation or other abnormalities in the intestine. If these tests show Crohn's disease, more x rays of both the upper and lower digestive tract may be necessary to see how much of the GI tract is affected by the disease.

The doctor may also do a visual exam of the colon by performing either a sigmoidoscopy or a colonoscopy. For both of these tests, the doctor inserts a long, flexible, lighted tube linked to a computer and TV monitor into the anus. A sigmoidoscopy allows the doctor to examine the lining of the lower part of the large intestine, while a colonoscopy allows the doctor to examine the lining of the entire large intestine. The doctor will be able to see any inflammation or bleeding during either of these exams, although a colonoscopy is usually a better test because the doctor can see the entire large intestine. The doctor may also do a biopsy, which involves taking a sample of tissue from the lining of the intestine to view with a microscope.