Let's Talk About Crohn's Disease Tests and Diagnosis

It would be great if a single exam could confirm if you have Crohn’s. Naturally, it’s not that simple—but the tests below can work together to provide a clearer picture of your health.

by Stephanie Wood Health Writer

Making a Crohn’s disease diagnosis is like working on a really challenging jigsaw puzzle: A lot of pieces need to fit together before the picture is clear. Those pieces include a combination of imaging and blood tests, as well as more nuanced info on how you’re feeling. As you head through the process, from initial questioning to the inevitable poking and prodding, we’re here to help you put the pieces together so you can get started on feeling better fast.

Crohn's Diagnosis

Our Pro Panel

We went to some of the nation’s top Crohn’s disease experts to bring you the most scientific and up-to-date information possible.

Jami Kinnucan, M.D.

Jami Kinnucan, M.D.

Gastroenterologist, IBD Specialist, and Assistant Professor of Medicine

University of Michigan School of Medicine

Ann Arbor, MI

Neilanjan Nandi

Neilanjan Nandi, M.D.

Director of the Inflammatory Bowel Disease Center

Drexel University School of Medicine


Frank I. Scott, M.D.

Frank I. Scott, M.D.

Gastroenterologist, IBD Specialist, and Assistant Professor of Medicine and Gastroenterology

University of Colorado School of Medicine

Aurora, CO

Crohn’s Disease Tests
Frequently Asked Questions
What is an endoscopy?

An endoscopy allows your doctor to look around inside your GI tract. In this procedure, a small camera is mounted on the end of a lighted, flexible tube known as a scope, which enters your body either through your mouth or anus. It can be uncomfortable and you may be given a painkiller or sedative in advance.

Can a blood test diagnose Crohn’s disease?

Unfortunately, no. There is no single test—blood or imaging—that can definitively prove someone has Crohn’s disease. However, blood tests are still important pieces of the puzzle. The clues they reveal can help support your diagnosis and will also be used to monitor disease activity, complications, and how well your medications are working.

Is there a test to predict if my Crohn’s disease will get worse?

No. Generally speaking, the chances of Crohn’s getting worse depend on how bad your symptoms were when you were diagnosed. (Fewer symptoms equals lower chance of the disease progressing.) Taking your medications as directed can help slow disease progression, as can cutting out smoking and alcohol.

How can I make bowel prep more bearable?

Talk with your doc: You might be able to add some flavoring to the chalky liquid you have to drink. Chilling it beforehand may help make it more palatable as well. You can also ask about taking some of the solution in pill form if you really struggle with drinking it. During the prep, treat your bottom to some soothing wet wipes instead of dry toilet paper, and wear loose fitting, easy-to-remove clothing.

What Is Crohn’s Disease Again?

Let’s review: Crohn’s disease causes inflammation of the digestive or gastrointestinal (GI) tract and can impact everything from your mouth (in the form of canker sores) to your anus. It’s most likely to strike in the small or large intestine, though, and is categorized as as an Inflammatory Bowel Disease (IBD) for the havoc it can wreak.

Crohn’s is triggered by the immune system’s white blood cells attacking your body’s healthy tissue. That produces inflammation, causing ulceration and tissue swelling that limits the intestine’s ability to process food, absorb nutrition, and eliminate waste. The result: Abdominal pain, diarrhea, and weight loss.

Crohn’s affects the same number of men and women. While it can occur at any age, it happens most frequently between the ages of 15 and 30, and again in your 50s and 60s.

All The Details on Crohn’s Disease

How Is Crohn’s Disease Diagnosed?

The frustrating reality: Crohn’s disease doesn’t fit into a nice neat box. There isn’t any single test that can diagnose it and symptoms vary from person to person. Symptoms can be similar to other gastrointestinal conditions, including ulcerative colitis, the other illness that falls under the IBD umbrella. There are also five different types of Crohn’s disease, categorized by their location within the GI tract, and each type can have differing symptoms.

If you suspect you have Crohn’s, start by seeing your primary care provider. It’s a good idea to write down a list of your symptoms so you don’t forget anything important. Bringing a friend or family member with you can reduce your stress and help you remember information. Your primary care doctor will evaluate your current medical history and family history, conduct a physical exam, and order initial bloodwork and stool testing to check for signs of inflammation, infection, anemia, and nutritional deficiencies—all indications of Crohn’s. These tests can also be used to rule out other issues that may be causing your symptoms.

About the Symptoms of Crohn’s Disease

What happens next? Your primary care provider will likely refer you to a gastroenterologist for further diagnosis. If not, you can go to a GI doc on your own (you can find one at crohnsandcolitisfoundation.org).

Top tip: While any gastroenterologist can treat Crohn’s disease, there are some who specialize in IBD and are more likely to be up on the latest treatments. Once you’re connected with a gastroenterologist, here are some of the likely tests you’ll receive:

Endoscopy Tests

Your gastroenterologist will want to take a look inside your GI tract and intestines. Fun! These tests will be a bit invasive—and might sound a little scary—but your healthcare team will minimize any discomfort. Since they’re outpatient procedures, you’ll go home the same day. If you need pain medication or anesthesia during the test, you’ll need someone to drive you home afterwards, so enlist the help of a friend or relative.

One thing to know: Several tests require a process known as bowel prep beforehand, which involves cleaning out the intestines with an oral solution and laxatives to give your doc a better view (we know, we know). It’s a dirty little secret of gastroenterologists: Having a colonoscopy is generally way easier than the bowel prep itself. If you have Crohn’s, you probably thought you pooped a lot already, but this takes the cake. All in the name of science, right? Your doctor will give you specific instructions, which typically involves drinking half the solution the night before the test, and the other half on test day.

In an endoscopy, a small camera mounted on the end of a lighted, flexible tube known as a scope is used to look inside the GI tract. Depending on the type of endoscopy you have, you may not be able to eat or drink anything after midnight before the test, you may need to do bowel prep beforehand, and you may be given a narcotic to prevent pain and a sedative to relax you. Types of endoscopy you may undergo include:

  • Esophagogastroduodenoscopy (EGD). That whopper of a word refers to a top-down test where the scope is inserted through your mouth to examine the lining of the esophagus, stomach, and all the way down to the first section of your small intestine, known as the duodenum.

  • Colonoscopy. This procedure is conducted from the bottom up. The scope is inserted through the anus and rectum to examine the large intestine and the end of the small intestine.

  • Sigmoidoscopy. The focus of this bottom up test is the lining of the lower third of the large intestine, which includes the rectum and the sigmoid colon.

  • Capsule enteroscopy. In this newer form of endoscopy, you swallow a small pill or capsule containing a miniature camera, which takes pictures of your large and small intestines as it travels through before being pooped out. Cool, right?

  • Balloon enteroscopy. An endoscopy with one or two balloons attached to help pull the endoscope through your intestine—may also be used.

  • Biopsy. Endoscopy procedures give your doctor the opportunity to take a pain-free biopsy—removing a small piece of intestinal tissue for further testing and analysis. It will then be sent to a lab where a pathologist will screen it for disease. Biopsies are also used for colorectal cancer screening, which you are at higher risk for if you have Crohn’s.

Imaging Tests

Some of the tests you may have include:

  • X-rays. These tests provide a picture inside the upper and lower GI tract. A standard x-ray can check for narrowing of the intestines or a blockage. Your doctor may also choose to do a contrast x-ray that can track the movement of a liquid known as barium through your intestines. You’ll be given the thick, chalky drink right before the test if the x-ray is of the small intestine. If your doctor is looking at the large intestine, you’ll be given a barium enema instead and you’ll need to do bowel prep beforehand. Barium can cause constipation, so you’ll need to drink plenty of fluids afterwards.

  • Enterography/enteroclysis. These tests take a peek at parts of your small intestine that can’t be seen by colonoscopy or endoscopy. You’ll need to drink an oral contrast solution that may taste mildly unpleasant (more fun!) that will then be viewed on a fluoroscopic x-ray (a type of x-ray that produces a continuous live image, like a movie), computed tomography (CT) scan, or magnetic resonance imaging (MRI) scan.

  • White blood cell scan (Leukocyte Scintigraphy). This imaging test tracks the presence of white blood cells, which are attracted to sites of inflammation. First, blood is drawn from your arm. White blood cells in the sample are tagged with a harmless radioactive substance, then the blood is injected back into your body and a special camera tracks them.

Blood Tests and Biomarkers

Your gastroenterologist may choose to do more extensive blood work to help with the diagnosis. Think of each type of blood test as another piece in the jigsaw puzzle you and your healthcare team are working to solve. The tests will also be used to provide clues about the activity of your disease and to see how well your medicines are working. Some of the routine blood tests for Crohn’s disease include:

  • Complete blood count (CBC). This test detects infection and anemia.

  • C-Reactive Protein (CRP) and Erythrocyte Sedimentation Rate (ESR). These tests detect levels of inflammation in the body.

  • Electrolyte panel. This test measures the levels of minerals such as potassium, which can drop with diarrhea.

  • Vitamin B12 levels. This test looks for low B12, a common deficiency when the small intestine isn't absorbing nutrients like it should.

  • Liver function. This test checks for liver and bile duct problems. Some medications may also be associated with liver test abnormalities.

A new generation of more sophisticated blood tests looks at proteins called antibodies, which are produced by the immune system. Commonly referred to as biomarkers, these antibodies help doctors differentiate between Crohn’s disease and ulcerative colitis—the other form of IBD that affects the GI tract. The two main antibodies are:

  • Anti-Saccharomyces cerevisiae antibodies (ASCA): More common in people with Crohn’s.

  • Perinuclear antineutrophil cytoplasmic antibodies (pANCA): More common in people with ulcerative colitis.

These biomarkers are helpful, but not entirely accurate in diagnosing your situation. For instance, some patients have neither antibody, while others who carry one type may actually have the opposite or neither disease.

Other potential biomarkers are on the horizon as well. A protein in the stool called calprotectin may predict relapse. High levels of C-reactive protein (CRP) have been shown to predict patients’ responses to biologic medications. And the anti-flagellin antibody CBir1 may be a marker of complications like fistulas or perforations. These biomarker tests may one day become an easy and inexpensive tool for diagnosing and monitoring Crohn’s, but more research is still needed.

After Your Diagnosis: What Happens Next?

Taking all these tests into consideration, along with your description of symptoms and how you feel, your doctor will determine if you have Crohn’s. If you do, get ready for more tests: Bloodwork, endoscopy, and images are needed on an ongoing basis to keep an eye on the status of the disease (is it active or in remission?) and to diagnose possible complications if your symptoms become more severe. To limit your exposure to radiation, your doctor will likely opt for MRIs over CT scans and x-rays.

You might think the tests we’ve talked about so far are plenty, but there’s more! To monitor your Crohn’s disease, you doctor may also have you undergo some of these procedures from time to time:

  • Chromoendoscopy. In this test, usually done during a colonoscopy, a blue dye is sprayed into the colon to highlight polyps and detect precancerous changes in the intestinal lining. Don’t freak, but you will poop blue afterward!

  • Endoscopic Ultrasound (EUS). An ultrasound probe attached to an endoscope looks deep below the lining of the intestines, usually to detect fistulae in the rectal area. These abnormal channels between different parts of the intestine and other organs can easily become infected, so it’s important to detect and treat them.

If all this sounds like a lot, well, it kind of is. But even though these tests can feel invasive and like they’re taking tons of your time, getting through them is the first step to identifying the problem and regaining control over your life.

Stephanie Wood
Meet Our Writer
Stephanie Wood

Stephanie Wood is a award-winning freelance writer and former magazine editor specializing in health, nutrition, wellness, and parenting.