Exams and Tests

Crohn's disease is diagnosed through a medical history and physical exam, imaging tests to look at the intestines, and laboratory tests.

Crohn's disease can be difficult to diagnose. The disease may go undiagnosed for years because symptoms usually develop gradually and the same part of the intestine is not always involved. Other diseases can also have the same symptoms as Crohn's disease. But Crohn's disease tends to cause the intestine to have a cobblestone appearance, which can help doctors diagnose it. The pattern results from the repeated formation and healing of sores (ulcers) in the intestine.

Tests used to diagnose Crohn's disease include:

• Flexible sigmoidoscopy or colonoscopy, in which a lighted viewing instrument is used to look at the inside of the colon. In general, colonoscopy is the preferred test because it can be used to examine the entire colon. Sigmoidoscopy reaches only the last part of the colon.
• Abdominal X-ray, which provides a picture of possible obstruction in the abdomen.
• Upper gastrointestinal (UGI) series with small-bowel follow-through to examine all of the small intestine. In this test the doctor examines the upper and part of the middle portions of the digestive tract. After you swallow a "shake" made of a white liquid (barium) and water, continuous X-rays (fluoroscopy) are taken to track the movement of the barium through the esophagus, stomach, and the small intestine. A video monitor displays the images.
• Upper gastrointestinal endoscopy, which allows your doctor to look at the interior lining of your esophagus, stomach, and duodenum with a thin, flexible imaging instrument called an endoscope.
• Barium enema, a test that allows the doctor to examine the large intestine (colon). For a barium enema, a white liquid (barium) is inserted through the rectum into the colon. The barium outlines the inside of the colon so that it can be more clearly seen on an X-ray.
• Computed tomography (CT) scan, which uses X-rays to produce detailed pictures of structures inside the body. A CT enterography may be done. This type of CT scan looks specifically at your small intestine for signs of Crohn's disease.
• Magnetic resonance imaging (MRI), which uses a magnetic field and pulses of radio wave energy to provide pictures of organs and structures inside the body.
• Standard blood tests and urine tests, which may be used to check for anemia, inflammation, or malnutrition. Depending on the symptoms, an erythrocyte sedimentation rate (ESR, or sed rate) or C-reactive protein (CRP) blood test may be done to look for infection or inflammation.

A biopsy of a sample of tissue from the lining of the intestine, collected during sigmoidoscopy or colonoscopy, can be used to confirm the diagnosis of Crohn's disease. A biopsy also may be done to find out whether a tumor is present. Multiple biopsies for cancer screening are often done in people who have had Crohn's disease of the colon or rectum for 8 years or more. Bowel biopsies are painless (other than the potential discomfort of the scope procedure) and remove only a tiny piece of tissue.

A stool analysis is often done, depending on symptoms, to look for blood, signs of bacterial infection, malabsorption, parasites, or the presence of white blood cells. This test can be used to distinguish Crohn's disease from irritable bowel syndrome (IBS), which is a less serious condition that sometimes has similar symptoms.

Other exams and tests that may also be used to evaluate Crohn's disease include:

• Video capsule endoscopy (VCE), in which you swallow a tiny camera that records its trip through your digestive tract by sending images to a recording device that you wear on a belt. Your doctor later examines the images by downloading them from the recording device. The camera passes out of your body in stool within 10 to 48 hours. VCE is particularly useful in examining the small intestine, which is difficult to see with other endoscopic tests.
• Small bowel enteroscopy, which uses a longer, lighted flexible tube with a tiny camera that sends pictures of the small intestine to a video screen. This helps the doctor look at the small intestine. The doctor can also take small samples (biopsy) of the tissue.
• Blood tests to find antibodies, which can sometimes help the doctor tell if you have Crohn's disease or ulcerative colitis. These tests include anti-neutrophil cytoplasmic antibody with perinuclear staining (pANCA), anti-Saccharomyces cerevisiae antibody (ASCA), and outer membrane porin C (Omp C).

Early Detection

No screening test exists for Crohn's disease at this time. But if you have had Crohn's disease affecting the colon or rectum for 8 years or longer, discuss with your doctor whether you need screening for colon cancer. Screening usually involves taking multiple-tissue biopsies during routine colonoscopy.