Testing and Diagnosis

Your doctor will likely diagnose Crohn’s disease or ulcerative colitis only after ruling out other possible causes for your signs and symptoms.

They will use a combination of tests and procedures to specifically test for signs of inflammatory bowel disease (IBD), including blood tests, endoscopic procedures, imaging (x-ray, ultrasound, CT, MRI), and/or a stool test. These tests, as well as therapeutic drug monitoring, can also be used to help track the course of your disease, inflammation, and response to medications. 

Below you will find more information about different types of tests and procedures used for diagnosis and disease monitoring. 

Differences between Crohn's disease and Ulcerative Colitis 

When thinking about diagnosis and testing, it is helpful to think about some of the differences between ulcerative colitis and Crohn’s disease

Ulcerative colitis 

  • Affects the colon (large intestine), always involving the rectum and extending upwards from there. 
  • Each patient differs in terms of how far up through the colon the colitis extends.

Crohn’s disease 

  • Crohn’s goes “from gum to bum.” It affects the entire digestive tract, including the esophagus, stomach, both the small and large intestines, and/or rectum. 
  • There can be normal the areas interspersed with areas that are affected (inflamed). 
  • Some people have disease that affects the upper gut, which includes the esophagus, stomach, and early part of the small intestine. 
  • Some have both small and large intestine involvement, and others only have disease in the large intestine or small intestine.

Endoscopic procedures

Ulcerative colitis (remember: it affects the rectum and large intestine only) can be assessed using colonoscopy. Crohn’s disease can be harder to evaluate this way because the small intestine is 22 feet long with many folds.


With Crohn’s disease, endoscopy can be used to view the top of the gut. Colonoscopy can be used to go backwards from the rectum all the way through the large intestine and into the last part of the small intestine. However, current colonoscopy and endoscopy techniques can only reach a small portion of the small intestine.

Capsule endoscopy

Capsule endoscopy is when you swallow a pill that contains a camera, which then travels through your digestive system taking pictures. Physicians do not use capsule endoscopy very much in Crohn’s disease because if there are any areas of narrowing along the digestive tract, the camera could become stuck. However, for some people, this test can be useful.

Imaging techniques

Barium x-ray

In a small intestine barium x-ray (also called “small bowel follow-through” or “small bowel meal”), you would drink a white, chalky liquid called barium. The barium allows for better visualization of the digestive tract with x-rays. As the barium flows through the digestive tract, the technician takes a series of pictures and sometimes video. This test is not used very much anymore.


One up-and-coming technology for evaluation of IBD is ultrasound, which uses high-frequency sound waves to create images. However, taking good quality ultrasound pictures of the intestine is a challenge and requires very specialized training. It involves a lot of detailed study and is not readily available in Canada.

CT enterography

A CT scan is a sophisticated x-ray device. Enterography is a word for taking pictures of the intestines. Sometimes the test is given with an intravenous contrast. CT enterography is quite common.

MR enterography

One promising technique for looking at the small intestine is MR enterography. This is the use of an MRI machine to take pictures of the intestines. MR enterography does not use radiation. 

In MR enterography, an MRI uses magnetic waves to take images of your insides. It involves a large machine with a tunnel inside. You would lie on your back and slide through the tunnel as the images are taken. 

Here are some steps you will need to take before having an MRI:
  • You need to remove all metal that can be magnetized, such as jewelry
  • Typically, you will need to drink some fluid (sometimes barium or sorbitol) before the test, which makes it easier to see the walls of the intestine 
  • You will also be given intravenous contrast called gadolinium, which is different from the contrast you might receive with a CT 

During the MRI, you may be asked every now and then to hold your breath. This allows you to hold still so they can take the series of pictures.

The images seen on MR enterography are very high resolution and show a lot of detail. One advantage of MR enterography (and also of CT) is it allows the radiologist to see the full thickness of the intestinal wall. This can be very useful information.

MR enterography shows inflamed areas of the intestines quite vividly with a white colour. MR enterography is also helpful for telling the difference between inflamed areas and scar tissue. 

Stool tests

Fecal calprotectin

Calprotectin is a protein found in white blood cells. When there is inflammation in your intestines, white blood cells will go to that area. When the white blood cells fight inflammation, they release their contents, including calprotectin. This results in higher levels of calprotectin in your stool. This test not only shows if there is inflammation; it can also measure how severe the inflammation is.
For patients who know they have IBD, this test can be used to find out if their disease is active or under control. The test is often used when a patient begins a new treatment, to see if it is working, as opposed to doing a colonoscopy. The test can also help determine which patients need to undergo further testing using colonoscopy.

For the family doctor, this test can be helpful in determining which patients with diarrhea need further testing for IBD.
Fecal calprotectin is a very practical test where the stool sample can be collected at home and mailed to the lab.

Therapeutic drug monitoring with blood tests

Therapeutic drug monitoring is used with biologic drugs such as infliximab. With these new medications, some patients have a great response at first, but over time they lose the response and the medication doesn’t work as well as it used to.
Biologics are given as an injection or infusion every few weeks. When the drug is first given, its level in the blood jumps up to what we call a “peak,” and over time that level drifts down to what we refer to as a “trough.” Then another dose is given and the level jumps up again. 

The trough level of a drug, just before the next dose, is actually very important and can help predict how well your disease is controlled. Patients who still have good levels of medication right before they get their next dose tend to do better than patients whose medication level is depleted before the next dose. 

People tend to clear out drugs from their system at different speeds. Some people actually make antibodies against the biologic which clears the drug out faster. If they clear out the drug too quickly, there is no drug left in their system and hence it cannot do its job very well. 

The doctor can test for both the level of drug immediately before the next dose, as well as whether the patient’s body has made antibodies against that drug. If the patient has a low level of drug and is not making antibodies, there is some other reason the drug is clearing out quickly, and the physician can help by giving more medication. 

If, on the other hand, there is a low level of drug and your body is making antibodies, there is probably no point continuing with that particular drug and it might be time to switch to a different medication. Also, if the drug level is high before the next infusion but the disease is not well-controlled, it might be time to switch medications.

What does the future hold?

There have been many improvements in the area of diagnostics and testing for IBD. In the future, it would be helpful to have ways to:

  • Predict which patients will have a more challenging disease course so we can put more resources into helping them
  • Figure out which drug matches which patient, so as to avoid excess trial and error
  • Have tests that can figure out if people have IBD before they even show symptoms, so we can do preventive care 

Want to Learn more about Testing and Diagnotics for IBD?

Watch a video presentation on diagnostics and testing led by an expert gastroenterologist at our Gutsy Learning Series

​Have you been recently DIAGNOSED with Crohn's or colitis?

If you have been recently diagnosed with Crohn's or colitis, visit our Newly Diagnosed page for more information and resources. 

strengthen your knowledge of living with crohn's and colitis

Visit the Living with Crohn's and Colitis section of our website to learn about diet and nutrition in IBD, treatment options, symptom management and other essential information.  

find a community near you

Your local chapter of Crohn’s and Colitis Canada is a powerhouse of health information and support. Through education, presentation and discussion, people can find resources to help them cope with their Crohn’s, and meet others who are living with Crohn’s or colitis.

Visit our Find My Community page to look up the chapter closest to you. It’s in your best interest to get active and informed!


  • Canada has among the highest incidence rates of Crohn's and colitis in the world.
  • 1 in 140 Canadians lives with Crohn’s or colitis.
  • Families new to Canada are developing these diseases for the first time.
  • Incidence of Crohn’s in Canadian kids under 10 has doubled since 1995.
  • People are most commonly diagnosed before age 30.

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