Diagnosis:

There is no definitive diagnostic test for Crohnâ ' s disease. A doctor will diagnose Crohnâ ' s disease based on medical history and physical examination, and the results of laboratory, endoscopic (appearance and biopsy results), and imaging tests.

Laboratory Tests

• Blood tests are used for various purposes, including to determine the presence of anemia. An increased number of white blood cells or elevated levels of inflammatory markers such as C-reactive protein may indicate the presence of inflammation.
• A stool sample may be taken and examined for blood, infectious organisms, or both.

Endoscopy

Flexible Sigmoidoscopy and Colonoscopy. Flexible sigmoidoscopy and colonoscopy are procedures that involve snaking a fiberoptic tube called an endoscope through the rectum to view the lining of the colon. The doctor can also insert instruments through it to remove tissue samples.

• Sigmoidoscopy, which is used to examine only the rectum and left (sigmoid) colon, lasts about 10 minutes and is done without sedation. It may be mildly uncomfortable, but it is not painful.
• Colonoscopy allows a view of the entire colon and requires a sedative, but it is still performed on an outpatient basis. It is important in differentiating between Crohn's disease and ulcerative colitis and in screening for colon cancer.

These procedures can help a doctor to distinguish between ulcerative colitis and Crohn's disease, as well as other diseases.

Wireless Capsule Endoscopy. Wireless capsule endoscopy (WCE) is a newer imaging approach that is sometimes used for diagnosing Crohn's disease. With WCE, the patient swallows a capsule containing a tiny camera that records and transmits images as it passes through the gastrointestinal tract.

Imaging Procedures

Upper and Lower Gastrointestinal Barium X-Rays. An upper gastrointestinal barium x-ray may be used if Crohn's disease is suspected in the small intestine. Swallowed barium passes into the small intestine and shows up on an x-ray image, which may reveal inflammation, ulcers, and other abnormalities.

Positron Emission Tomography (PET) and Computed Tomography (CT) Scans. PET/CT scans are being investigated as a non-invasive method for evaluating active IBD.

Ruling Out Diseases Resembling Crohn's Disease

Ulcerative Colitis. Diarrhea associated with ulcerative colitis tends to be more severe than diarrhea caused by Crohnâ ' s disease. Abdominal pain is more constant with Crohnâ ' s disease than with ulcerative colitis. Fistulas are common with Crohnâ ' s disease but very rare with ulcerative colitis. Endoscopy and imaging tests often reveal more extensive involvement through the entire gastrointestinal tract with Crohnâ ' s disease than with ulcerative colitis.

Irritable Bowel Syndrome. Irritable bowel syndrome (IBS), also known as spastic colon, functional bowel disease, and spastic colitis causes some of the same symptoms as inflammatory bowel disease (IBD). (However, it is NOT the same as inflammatory bowel disease.) Bloating, diarrhea, constipation, and abdominal cramps are all symptoms of IBS. Irritable bowel syndrome is not caused by inflammation, however, and no fever or bleeding occurs. Behavioral therapy may be helpful in treating IBS. (Psychological therapy does not improve inflammatory bowel disease.)

Celiac Sprue. Celiac sprue, or celiac disease, is an intolerance to gluten (found in wheat) that triggers inflammation in the small intestine and causes diarrhea, vitamin deficiencies, and stool abnormalities. It occurs in some people with inflammatory bowel disease and is usually first noticed in children.

Acute Appendicitis. Crohn's disease may cause tenderness in the right lower part of the abdomen, where the appendix is located, that resembles an appendicitis.

Cancer. Colon or rectal cancers must always be ruled out when symptoms of IBD occur.

Intestinal Ischemia (Ischemic Colitis). Symptoms similar to IBD can be caused by blockage of blood flow in the intestine. This is more likely to occur in elderly people.