How Crohn's Disease Is Diagnosed

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Crohn's disease is a type of inflammatory bowel disease (IBD) that is characterized by inflammation of the gastrointestinal tract.

Recognizing the symptoms of Crohn's is important, but only a doctor can make an official diagnosis of Crohn's.

This article discusses different tests used to diagnose Crohn's disease.

doctor performing endoscopy

Joos Mind / Getty Images

Physical exam

Along with taking a complete medical history, a physical exam will be one of the first diagnostic tools a healthcare provider will use to determine the cause of symptoms.

As part of a physical exam, a person may be asked to lie down on the examination table. The healthcare provider will then use their hands to tap and press the abdomen. Doing this allows a healthcare provider to:

  • Check if the abdomen is bloated
  • Check for tenderness
  • Check for pain
  • Determine if the liver is enlarged
  • Determine if the spleen is enlarged

A healthcare provider may also use a stethoscope to listen for sounds.

Lab tests

A healthcare provider may order a series of laboratory tests to assist in a diagnosis of Crohn's disease.

Blood tests

Blood tests allow doctors to determine if there have been changes in red or white blood cells:

  • Lower amounts of red blood cells than normal, or smaller blood cells, may be indicative of anemia.
  • If the white blood cell count is higher than typical, this may indicate inflammation or an infection. 

Stool tests

A stool test involves analyzing a sample of stool (feces). These tests are performed to exclude other digestive diseases or causes of gastrointestinal symptoms.

Imaging scans

Imaging scans are noninvasive procedures that enable physicians to capture images of affected parts of the gastrointestinal tract.

Below are imaging tests that can be used.

CT Scan

A CT scan uses powerful X-ray technology to take images of the digestive tract.

During this procedure, a special drinking solution may be given, along with an injection of a special kind of dye called contrast medium. This allows a healthcare provider to more easily see the structures in the digestive tract during the procedure.

During a CT scan, the patient lies on a table that is then moved into a tunnel-like machine that takes X-ray images.

Double Contrast Barium Enema X-Ray

During this procedure, a contrast is used to highlight certain areas of the gastrointestinal tract. The right colon and the ileum (a part of the small intestine) can be seen during this test.

Preparations are needed before the procedure to remove stool from the colon. This may be done through an enema, laxative, or a liquid diet.

During the procedure, a contrast material called a barium preparation is inserted into the body using a rectal tube. This contrast material then helps outline the colon and highlights abnormalities.

At that time, an X-ray is taken and the doctor examines the images to look for signs of Crohn's disease.

Small Bowel Series

This noninvasive test is performed to visualize the small bowel.

During the small bowel series procedure, a barium preparation is consumed by mouth. X-rays are then taken at regular intervals.

Once the barium preparation has reached the small intestine, a specialized X-ray called a fluoroscopy is performed. This type of X-ray takes moving images of the internal structures of the small intestine.

Once the procedure is over, X-ray images show any obstructions and the extent of Crohn's disease.

Endoscopy

An endoscopy is the most accurate way of diagnosing Crohn's disease. An endoscopy can also help doctors exclude other conditions like cancer, diverticular disease, or ulcerative colitis.

There are two kinds of endoscopy used in the diagnosis of Crohn's disease.

Upper GI Endoscopy and Enteroscopy

During an upper GI endoscopy, a physician uses an endoscope to examine the upper areas of the digestive tract.

This procedure is performed at a hospital or a specialist outpatient center. Typically, an anesthetic is used to numb the throat alongside a light sedative to keep the patient relaxed throughout the procedure.

Once the anesthetic has been used, a doctor gently moves the endoscope down the esophagus into the stomach and duodenum (the first part of the small intestine).

An enteroscopy is similar but involves the use of a longer endoscope to examine the small intestine.

Capsule Endoscopy

A capsule endoscopy differs from an upper GI endoscopy because it doesn't require time in the hospital or the use of an anesthetic.

During this procedure, a capsule containing a small camera is swallowed and moves through the digestive tract. When the capsule travels throughout the digestive tract, it takes images and transmits these to a special receiver device worn during the procedure.

The capsule containing the camera exits the body during a bowel movement.

Once the test is over, the doctor can download the images and review them.

Flexible Sigmoidoscopy

A flexible sigmoidoscopy is a procedure used to examine the lower part of the colon and the rectum.

During this test, a flexible tube with a light called a sigmoidoscope is inserted into the body to examine the affected area of the GI tract.

A flexible sigmoidoscopy requires the colon to be free of stool to allow for good visibility. This may be achieved through an enema, laxatives, or a liquid diet prior to the procedure.

During the procedure, the sigmoidoscope is inserted into the body and into the large intestine. The test may cause cramping or discomfort. Biopsy forceps may be used to take a sample of tissue for analysis.

Colonoscopy

A colonoscopy may be performed to determine the progression and extent of Crohn's disease.

A colonoscopy allows a doctor to examine the entire colon and the rectum. A colonoscopy visualizes more of the bowel than a sigmoidoscopy.

As with a sigmoidoscopy, the colon must be clear of stool, and will require preparation prior to the procedure.

Sedation is given prior to the procedure. The colonoscope is inserted through the rectum and anus to the large intestine. A camera allows the doctor to see the inside of the large intestine. A sample of tissue may be taken using special biopsy forceps.

Like a sigmoidoscopy, a colonoscopy may cause discomfort and cramping.

what to expect during a colonoscopy diagram

Cindy Chung / Verywell

Chromoendoscopy

During a colonoscopy, the doctor may wish to also perform a chromoendoscopy to check for precancerous changes and polyps.

During this procedure, a blue dye is sprayed inside the colon to highlight any changes to the lining of the intestine. If polyps are found they can be removed or a biopsy may be taken.

A Word From Verywell

Reaching a diagnosis of Crohn's disease can be a lengthy process. As the symptoms of Crohn's can be similar to other conditions, first other diseases need to be excluded.

There is no singular test to diagnose Crohn's and typically a combination of tests are performed to reach an official diagnosis. If you are concerned about any symptoms you are experiencing, or suspect you may have Crohn's, you should speak with a healthcare provider.

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3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Crohn's and Colitis Foundation. Signs and symptoms of Crohn's disease.

  2. National Institute of Diabetes and Digestive and Kidney Diseases. Diagnosis of Crohn’s disease. Updated September 2017.

  3. Johns Hopkins Medicine. Crohn's disease.