Blood and Antibody Tests
Crohn's disease can cause diarrhea and abdominal pain, but these symptoms can be caused by other conditions as well. One of the first tests performed if Crohn's disease is suspected is a blood test. According to the Mayo Clinic, a routine battery of blood tests are often done for patients who have Crohn's disease. These tests look for anemia (which can be caused by blood loss resulting from Crohn's disease) and make sure that the intestinal symptoms are not caused by an infection. Crohn's disease is an autoimmune disease, which means that it is caused by the immune system making antibodies that attack the healthy tissue of the intestines. Doctors can also test blood samples of Crohn's patients to look for these antibodies.
Endoscopy
Another way of diagnosing Crohn's disease is to actually look at the inside of the intestines. This can be done using endoscopy, which makes use of a small, flexible camera to look at the insides of the digestive system. The Crohn's and Colitis Foundation of America notes that many kinds of endoscopy can be performed. Sigmoidoscopy, for example, allows physicians to view the lower one-third of the colon, whereas a colonoscopy allows for the visualization of all of the colon. Another option is called capsule endoscopy, in which the patient swallows a small camera that is shaped like a capsule. This capsule camera then travels through the digestive system, taking multiple images, which are then sent to a recorder. This allows for the visualization of the digestive system to look for some of the characteristic lesions and damaged areas that are caused by Crohn's disease.
Other Imaging Techniques
Doctors can also diagnose Crohn's disease by imaging the digestive system in ways that do not involve a camera. One way is by taking an X-ray, which can be used to get a picture of the intestines' structure. Typically, patients need to drink a solution of barium beforehand to absorb the X-ray beams during the procedure. This allows doctors to look for inflammation of the intestinal walls that causes them to become thicker and narrows the space in the intestines. Sometimes patients receive a CT scan, which is similar to an X-ray but gives more detailed information about the interior of the body.
