Crohn’s disease and ulcerative colitis are not the same, but they are similar, and many of the same tests are run in order for the doctor to make an accurate diagnosis. The following tests focus on examination of the large intestine (colon), but tests to look at the small intestine may be helpful if the doctor wants to rule out Crohn’s disease.

Crohn’s is a bit trickier to diagnose, because the inflammation can be patchy and can affect any portion of the gastrointestinal tract from the mouth to the anus. Ulcerative colitis is limited to the colon and the inflammation is continuous, which makes the diagnosis slightly more straight-forward.

Blood and stool tests

Blood and stool tests are often run as one of the first diagnostic exams when a doctor suspects ulcerative colitis. These test cannot be used alone to diagnose ulcerative colitis, but they are helpful in ruling out other causes of symptoms. The doctor will check for anemia and signs of infection in the blood, as well as hidden blood in the stool. The doctor will rule out bacterial infections or parasitic infections that could also cause inflammation of the bowels.


A colonoscopy is a test where the doctor inserts a tube (called a colonoscope) into the rectum to examine the large intestine and the last part of the small intestine. This is the most important and useful exam to diagnose all forms of IBD, because it gives full visualization of the colon and rectum. The doctor can take pictures and small tissue samples (biopsies) to look for inflammation.

The procedure is not painful and you will be asleep during the procedure. You will be taken care of by the entire endoscopy team including pediatric nurses, pediatric anesthesia doctors, child life specialists and your gastroenterologist.

On the day before the colonoscopy, you will need to drink medicines to help you get rid of most of the stool in your intestines. This helps the doctor see the lining of your bowel. You will need to eat lighter meals on the day before, using instructions from our office. Talk with your doctor if you have any questions.

Flexible Sigmoidoscopy

A flexible sigmoidoscopy can be thought of as a partial colonoscopy. It allows the doctor to closely examine the sigmoid colon, which is the last part of the colon (closest to the rectum and anus).