How is the disease diagnosed?

Crohn's disease is diagnosed through medical history, physical examination, and laboratory tests. There is no one test or feature of the disease that confirms the diagnosis. Sigmoidoscopy is a procedure to examine the rectum and part of the large intestine. It involves passing a small telescope through the anus so that the rectum and large intestine can be seen directly. This procedure is very important if a person has long-term diarrhea or bloody diarrhea.

A blood test called a complete blood count, or CBC, may show anemia, a low level of red blood cells. Lab studies may also show abnormal liver function and low levels of certain vitamins and minerals. There may also be evidence of poor food absorption.

Another common test is the barium enema. In this test, a contrast agent called barium is injected into the intestine and X-rays are taken. Sometimes the diagnosis is made during surgery that is performed to find the cause of severe abdominal pain.