Diagnosis of Crohn's Disease
Because the symptoms of Crohn's disease are similar to other inflammatory bowel diseases, particularly ulcerative colitis, doctors must evaluate symptoms carefully and rule out other causes before diagnosing the condition. This process is called differential diagnosis.
In many cases, a final diagnosis of Crohn's disease takes some time to reach. The diagnosis usually involves taking the patient's medical history. Crohn's disease often is inherited, so an analysis of family history is important, along with a review of past medical issues, surgeries, medications, diet, lifestyle habits, and a history of symptoms. In a physical examination, the physician looks for signs of fissures or fistulas, and other indications of inflammatory bowel disease.
Diagnostic Tests for Crohn's Disease
A number of diagnostic tests can help physicians determine if a patient has Crohn's disease. Blood tests can be used to detect low red blood cell counts, which indicate anemia and inflammation, and low levels of electrolytes and the protein albumin, which may indicate malnourishment. If Crohn's disease is suspected, levels of other proteins and substances in the blood can provide clues about how active the inflammation is.
Imaging tests can indicate where the disease is concentrated, how far it has spread, and whether any complications have developed. The most common tests include the following:
- Endoscopy—In this test, the physician uses a flexible, lighted tube with a camera attached to take pictures of various locations in the digestive tract. Endoscopy provides information about inflammation, bleeding, and other problems. When this test is performed in the lower digestive tract, it is called a colonoscopy. When only the upper part of the digestive tract is examined, it is called an upper endoscopy.
- Barium contrast studies—In these tests, x-rays are used to determine the location and severity of the inflammation. Prior to the test, patients drink a contrast substance called barium, which provides better images of the small intestine than regular x-rays. A small bowel follow-through, which focuses on the small intestine, can show images that are not detected in a standard colonoscopy. Sometimes, a barium enema is performed if Crohn's disease of the colon and rectum is suspected.
- CT scan, ultrasound, or MRI scan—These tests can be used to detect complications of Crohn's disease, such as abscesses, fistulas, or problems with the liver, kidneys, or bile duct.
In some cases, the physician performs a biopsy. In this procedure, a sample of tissue is removed surgically and studied under a microscope.