Your doctor makes the diagnosis of inflammatory bowel disease based on your symptoms and various exams and tests:
Stool exam. You'll be asked for a stool sample that will be sent to a laboratory to rule out the possibility of bacterial, viral, or parasitic causes of diarrhea. In addition, the stool will be examined for traces of blood that cannot be seen with the naked eye.
Complete blood count. A nurse or lab technician will draw blood, which will then be tested in the lab. An increase in the white blood cell count suggests the presence of inflammation. And if you have severe bleeding, the red blood cell count and hemoglobin level may decrease.
Other blood tests. Electrolytes (sodium, potassium), protein, and markers of inflammation, such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), may be drawn to look at disease severity. Perinuclear antineutrophil cytoplasmic antibody (pANCA) levels may be up in ulcerative colitis. In addition, specific tests for sexually transmitted diseases may be done.
Barium X-ray. Although seldom used, it can check the upper gastrointestinal (GI) tract -- the esophagus, stomach, and small intestine -- for abnormalities caused by Crohn's disease. You swallow a chalky white solution that coats the intestinal tract so it will be visible on X-rays. If a barium study is used to check the lower GI tract, you will be given an enema containing barium and asked to hold it in while X-rays are taken of the rectum and colon. Abnormalities caused by either Crohn's or ulcerative colitis may show up in these X-rays.
Sigmoidoscopy. In this procedure, a doctor uses a sigmoidoscope, a narrow, flexible tube with a camera and light, to visually examine the last one-third of your large intestine, which includes the rectum and the sigmoid colon. The sigmoidoscope is inserted through the anus and the intestinal wall is visually examined for ulcers, inflammation, and bleeding. The doctor may also take samples -- biopsies -- of the intestinal lining with an instrument inserted through the tube. These will then be examined in a laboratory under a microscope.
Colonoscopy. A colonoscopy is similar to a sigmoidoscopy, except that the doctor will use a colonoscope, a longer flexible tube, to examine the entire colon. This procedure gives you a look at the extent of disease in the colon.
Upper endoscopy. If you have upper GI symptoms such as nausea and vomiting, a doctor will use an endoscope, a narrow, flexible tube with a camera and light, that will be inserted through the mouth -- to examine your esophagus, stomach, and duodenum, which is the first part of your small intestine. Ulceration occurs in the stomach and duodenum in up to one out of every 10 people with Crohn's disease.
Capsule endoscopy. This test may be helpful to diagnose disease in the small intestine, such as in Crohn’s disease. You swallow a small capsule that has a camera in it. Pictures are taken of the esophagus, stomach and small bowel and then sent to a receiver you wear on a belt. At the end of the procedure, the pictures are downloaded from the receiver onto a computer. The camera is passed through your body into the toilet.