How Is Inflammatory Bowel Disease Diagnosed?

Reviewed by: HU Medical Review Board | Last reviewed: April 2024 | Last updated: April 2024

An accurate diagnosis can be the first step toward successful treatment for inflammatory bowel disease (IBD). Unfortunately, there is no single test that can be used to diagnose IBD. IBD includes 2 conditions: Crohn's disease and ulcerative colitis (UC). Both are characterized by inflammation in the bowels. Doctors must use a variety of tests, exams, and imaging to diagnose both conditions.1,2

If you have symptoms of either Crohn’s disease or UC, your doctor will start by asking about your medical history and doing a physical exam. If they suspect you have IBD, they may move on to other tests or processes. These may include:1-4

  • Blood or stool tests
  • Endoscopic procedures
  • Imaging tests

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Medical history and physical exam

IBD diagnosis typically starts with a medical history. This also helps your doctor rule out other conditions. Questions may cover your overall health, diet, family history, and bowel routine.2,3

The next step is usually a standard physical exam. This exam may include a rectal exam. During a rectal exam, your doctor will use a gloved, lubricated finger to examine the inside of your rectum. The goal is to feel for anything unusual and to check for blood in the stool.2,5

Blood or stool tests

Blood tests and stool tests can be used to detect signs of IBD. They also can help determine whether your symptoms are linked to Crohn’s, UC, or some other cause.1-3

Blood tests can look for anemia, or a low red blood cell count. Anemia can be a sign of IBD. Stool tests may look for signs of blood, bacteria, or parasites. The presence of bacteria or parasites would indicate a different condition.1-3

Endoscopic procedures

Endoscopic procedures use small cameras to look inside your colon or intestine. There are several types that may be used to diagnose IBD:1-3,6

  • Colonoscopy – In this procedure, the doctor uses a thin, flexible tube with a camera and light to view the whole colon. The colon is the lowest part of the large intestine. The tube is inserted through the anus. A colonoscopy helps your doctor look for any signs of IBD. Your doctor may also take a small tissue sample, called a biopsy.
  • Sigmoidoscopy – This procedure is similar to a colonoscopy but uses a shorter tube. It only looks at your lower large intestine.
  • Upper endoscopy – Here, the doctor uses a thin tube and camera to look at the upper part of your digestive system. The camera can go as far down as the beginning of the small intestine.
  • Capsule endoscopy – In this test, you swallow a capsule with a small camera in it. This capsule takes pictures as it travels through your upper and lower gastrointestinal (GI) tract.

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Imaging tests

Your doctor may also use imaging tests to help diagnose IBD. These can be less invasive than endoscopic procedures. Possible imaging tests for IBD include:1-4

  • X-rays – X-rays of the GI tract may show whether there is inflammation.
  • Computerized tomography (CT) scans – A CT scan is a special type of X-ray that is more detailed. You may be given a special drink before a CT scan that helps the machine capture more details. This is called a CT enterography.
  • Magnetic resonance imaging (MRI) – MRIs can take detailed images of organs and tissues. Variations of MRIs include an MR enterography or pelvic MRI.

Diagnosing Crohn’s disease versus ulcerative colitis

Crohn’s disease can impact any part of the digestive tract between the mouth and anus. But UC affects only the colon. In Crohn’s, there may be healthy parts of the intestine next to inflamed areas. In UC, the entire colon is usually inflamed.2,7

Doctors can use these signs to make a diagnosis from test results. For example, doctors may use a colonoscopy to rule out CD.2,7

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