What is Crohn’s disease?

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. They 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:

Your doctor will need to perform a physical examination and obtain information about your medical history. This will include 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.

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. The blood tests will also help detect 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. Combined with other test results, blood tests will help your doctor evaluate your exact condition.

Stool test

You may be asked to supply a stool sample to test for the presence of blood or signs of infection. The 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 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, another name for the large intestine, which includes the rectum. You will undergo this test 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. This allows for a greater contrast between specific areas and provides 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 doctor will insert the tube through your mouth to examine the upper portion of your digestive tract, which includes your mouth, esophagus, stomach, and the first part of your small intestine, called the duodenum.

Upper GI series

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


For a colonoscopy, your doctor will insert an endoscope into your rectum to examine your entire colon. If a biopsy of the colon lining finds clusters of inflammatory cells, called granulomas, it will help to confirm a diagnosis of Crohn’s disease. You may have Crohn’s disease and not have granulomas. You may also 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 it examines only the sigmoid colon, the last section of your colon.


During any of the following procedures, your doctor may take small tissue samples to look at under a microscope.

  • colonoscopy
  • endoscopy
  • sigmoidoscopy

This is called a biopsy. A biopsy can identify different types of inflammation and detect cancer or dysplasia, or 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. It also helps the doctor look for:

  • blockages
  • abscesses, or infection
  • fistulas, or 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.

A diagnosis of Crohn’s disease usually requires that you have certain symptoms, and that results of a combination of the above tests confirm that diagnosis. An accurate diagnosis is the first step in treating your illness and relieving your symptoms.