How Your Doctor Diagnoses Crohn’s Disease

Written by Michael Kerr | Published on July 1, 2014
Medically Reviewed by Kenneth R. Hirsch, MD on July 1, 2014

Diagnosing Crohn’s disease depends on several factors. Learn how your doctor diagnoses Crohn's and what the first step is after that.

Crohn’s disease is one of a group of disorders called inflammatory bowel diseases (IBDs). These illnesses involve inflammation and irritation of the gastrointestinal (GI) tract and have many symptoms in common. In some cases, Crohn’s is difficult to distinguish from ulcerative colitis, another inflammatory bowel disease. The symptoms of Crohn’s also resemble those of other GI disorders such as irritable bowel syndrome, diverticulitis, and colon cancer.

Diagnosis of Crohn’s Disease

Your doctor will need to perform a physical examination and obtain information about your medical history. He or she will also ask questions about your family medical history.

Your doctor will want to rule out infection and other GI disorders.

There is no single test for Crohn’s disease. The diagnosis is based on an evaluation of your symptoms and results of a number of tests. If your symptoms indicate that you might have Crohn’s disease, your doctor will probably perform a variety of tests.

Tests Used to Diagnose Crohn’s Disease

The following tests will help your doctor determine if you have Crohn’s disease.

Blood Tests

Blood tests will indicate if you have anemia (which might occur with GI bleeding) or an infection. Anemia and infections can both occur either with or without Crohn’s disease. Their presence or absence alone is not enough to provide a diagnosis. In conjunction with other test results, blood tests will help your doctor evaluate your exact condition.

Stool Testing

You may be asked to supply a stool sample to test for the presence of blood or signs of infection. As with blood tests, these results will be evaluated along with the results of other tests.

Breath Test

A breath test can identify lactose intolerance. When undigested lactose is metabolized in the colon, bacteria there release hydrogen into the bloodstream which can then be measured in your breath. You may have lactose intolerance with or without Crohn’s disease. However, lactose intolerance is common with Crohn’s disease. If you have Crohn’s disease and lactose intolerance, consuming milk and milk products can make your symptoms worse.

Barium Enema

A barium enema is an X-ray of the colon (large intestine) including the rectum. This test is performed in a doctor's office or a hospital. You will be given an enema using a special chalky liquid called barium sulfate that coats the large intestine, allowing for a greater contrast between specific areas and providing clearer X-rays.

Upper Endoscopy

An endoscope is a thin flexible tube with a small camera mounted on the end. For an upper endoscopy, the tube is inserted through the mouth so your doctor can examine the upper portion of your digestive tract—your mouth, esophagus, stomach, and the first part of your small intestine (duodenum).


For a colonoscopy, your doctor will use an endoscope inserted rectally to examine your entire colon. If a biopsy of the colon lining finds clusters of inflammatory cells (granulomas), it will help to confirm a diagnosis of Crohn’s disease. You may have Crohn’s disease and not have granulomas. Furthermore, you may have Crohn’s disease in another part of your digestive tract that cannot be seen during a colonoscopy.


A sigmoidoscopy is similar to a colonoscopy but examines only the sigmoid colon, the last section of your colon.


During a colonoscopy, endoscopy, or sigmoidoscopy, your doctor may take small tissue samples to look at under a microscope. This is called a biopsy. This can identify different types of inflammation and detect cancer or dysplasia (abnormal cells).

CT Scan

A computed tomography (CT) scan is a special X-ray that uses computer technology to create a three dimensional image. You may be asked to drink a special dye for this procedure. The CT scan helps your doctor assess the extent and location of disease as well as look for blockages, abscesses (infection), and fistulas (abnormal tunnels through tissue).

Capsule Endoscopy

For this procedure, you will swallow a capsule that contains a camera with a battery, light, and transmitter. As it works its way through your digestive system, the camera takes pictures and transmits them to a computer you wear on your belt. When it has finished its journey, it is passed in your stool. This procedure is generally very safe. However, if you have an intestinal blockage, the camera may become stuck and need to be removed surgically. The pictures taken by this procedure are usually not clear enough for a final diagnosis.

Magnetic Resonance Imaging (MRI)

An MRI uses radio waves and magnetic fields to produce images of your internal organs. It can help your doctor identify areas of narrowing and inflammation that are common in Crohn’s disease.

Upper GI Series

For an upper GI series, the patient drinks barium and X-rays are taken of the small intestine.

A diagnosis of Crohn’s disease usually requires a combination of symptoms and results of some combination of the above tests. Accurate diagnosis is the first step in treating your illness and relieving your symptoms.

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Show Sources

  • About Crohn's Disease. (n.d.). Home. Retrieved February 1, 2012, from
  • Crohn's disease: MedlinePlus Medical Encyclopedia. (2010, December 13). National Library of Medicine - National Institutes of Health. Retrieved January 26, 2012, from ​
  • Crohn's Disease - National Digestive Diseases Information Clearinghouse. (n.d.). Home - National Digestive Diseases Information Clearinghouse. Retrieved January 28, 2012, from
  • Saibil, F. G. (2011). Crohn's disease and ulcerative colitis: everything you need to know : the complete practical guide (3rd ed.). Richmond Hill, Ont.: Firefly Books.
  • Steinhart, A. H., Roberts, J., & Maunder, B. (2006). Crohn's & colitis: understanding and managing IBD. Toronto: R. Rose.
  • Warner, A. S., & Barto, A. E. (2010). 100 questions & answers about Crohn's disease and ulcerative colitis: a Lahey Clinic guide (2nd ed.). Sudbury, Mass.: Jones and Bartlett Publishers.

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