Diagnosis of Crohn’s Disease

How do doctors diagnose Crohn’s disease?

Doctors typically use a combination of tests to diagnose Crohn’s disease. Your doctor will also ask you about your medical history—including medicines you are taking—and your family history and will perform a physical exam.

Physical exam

During a physical exam, a doctor most often

  • checks for bloating in your abdomen
  • listens to sounds within your abdomen using a stethoscope
  • taps on your abdomen to check for tenderness and pain and to see if your liver or spleen is abnormal or enlarged

Diagnostic tests

Your doctor may use the following tests to help diagnose Crohn’s disease:

  • lab tests
  • intestinal endoscopy
  • upper gastrointestinal (GI) series
  • computed tomography (CT) scan

Your doctor may also perform tests to rule out other diseases, such as ulcerative colitis, diverticular disease, or cancer, that cause symptoms similar to those of Crohn’s disease.

What tests do doctors use to diagnose Crohn’s disease?

Your doctor may perform the following tests to help diagnose Crohn’s disease.

Lab tests

Lab tests to help diagnose Crohn’s disease include:

Blood tests. A health care professional may take a blood sample from you and send the sample to a lab to test for changes in

  • red blood cells. If your red blood cells are fewer or smaller than normal, you may have anemia.
  • white blood cells. When your white blood cell count is higher than normal, you may have inflammation or infection somewhere in your body.
Image of a nurse taking blood
Blood test

Stool tests. A stool test is the analysis of a sample of stool. Your doctor will give you a container for catching and storing the stool. You will receive instructions on where to send or take the kit for analysis. Doctors use stool tests to rule out other causes of digestive diseases.

Intestinal endoscopy

Intestinal endoscopies are the most accurate methods for diagnosing Crohn’s disease and ruling out other possible conditions, such as ulcerative colitis, diverticular disease, or cancer. Intestinal endoscopies include the following:

Colonoscopy. Colonoscopy is a procedure in which a doctor uses a long, flexible, narrow tube with a light and tiny camera on one end, called a colonoscope or endoscope, to look inside your rectum and colon. The doctor may also examine your ileum to look for signs of Crohn’s disease.

A trained specialist performs a colonoscopy in a hospital or an outpatient center. A health care professional will give you written bowel prep instructions to follow at home before the procedure. You will receive sedatives, anesthesia, or pain medicine during the procedure.

During a colonoscopy, you’ll be asked to lie on a table while the doctor inserts a colonoscope into your anus and slowly guides it through your rectum and colon and into the lower part of your ileum. If your doctor suspects that you have Crohn’s disease, the colonoscopy will include biopsies of your ileum, colon, and rectum. You won’t feel the biopsies.

Upper GI endoscopy and enteroscopy. In an upper GI endoscopy, your doctor uses an endoscope to see inside your upper digestive tract, also called your upper GI tract.

A trained specialist performs the procedure at a hospital or an outpatient center. You should not eat or drink before the procedure. A health care professional will tell you how to prepare for an upper GI endoscopy. You most often receive a liquid anesthetic to numb your throat and a light sedative to help you stay relaxed and comfortable during the procedure.

During the procedure, the doctor carefully feeds the endoscope down your esophagus and into your stomach and duodenum.

During an enteroscopy, a doctor examines your small intestine with a special, longer endoscope using one of the following procedures:

  • push enteroscopy, which uses a long endoscope to examine the upper portion of your small intestine
  • single- or double-balloon enteroscopy, which uses small balloons to help move the endoscope into your small intestine
  • spiral enteroscopy, which uses a tube attached to an endoscope that acts as a corkscrew to move the instrument into your small intestine

Capsule endoscopy. In capsule endoscopy, you swallow a capsule containing a tiny camera that allows your doctor to see inside your digestive tract. You should not eat or drink before the procedure. A health care professional will tell you how to prepare for a capsule endoscopy. You don’t need anesthesia for this procedure.

The test begins in a doctor’s office, where you swallow the capsule. You can leave the doctor’s office during the test. As the capsule passes through your digestive tract, the camera will record and transmit images to a small receiver device that you wear. When the recording is done, your doctor downloads and reviews the images. The camera capsule leaves your body during a bowel movement, and you can safely flush it down the toilet.

Upper GI series

An upper GI series is a procedure in which a doctor uses x-rays, fluoroscopy, and a chalky liquid called barium to view your upper GI tract.

An x-ray technician and a radiologist perform this test at a hospital or an outpatient center. You should not eat or drink before the procedure. A health care professional will tell you how to prepare for an upper GI series. You don’t need anesthesia for this procedure.

For the procedure, you’ll be asked to stand or sit in front of an x-ray machine and drink barium. The barium will make your upper GI tract more visible on an x-ray. You will then lie on the x-ray table, and the radiologist will watch the barium move through your upper GI tract on the x-ray and fluoroscopy.

CT scan

A CT scan uses a combination of x-rays and computer technology to create images of your digestive tract.

For a CT scan, a health care professional may give you a solution to drink and an injection of a special dye, called contrast medium. Contrast medium makes the structures inside your body easier to see during the procedure. You’ll lie on a table that slides into a tunnel-shaped device that takes the x-rays. CT scans can diagnose both Crohn’s disease and the complications of the disease.

November 2016
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This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. The NIDDK translates and disseminates research findings through its clearinghouses and education programs to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by the NIDDK is carefully reviewed by NIDDK scientists and other experts.