Crohn’s disease is a disease that causes inflammation, or swelling, and irritation of any part of the digestive tract—also called the gastrointestinal (GI) tract. The part most commonly affected is the end part of the small intestine, called the ileum.
The GI tract is a series of hollow organs joined in a long, twisting tube from the mouth to the anus. The movement of muscles in the GI tract, along with the release of hormones and enzymes, allows for the digestion of food.
In Crohn’s disease, inflammation extends deep into the lining of the affected part of the GI tract. Swelling can cause pain and can make the intestine—also called the bowel—empty frequently, resulting in diarrhea. Chronic—or long-lasting—inflammation may produce scar tissue that builds up inside the intestine to create a stricture. A stricture is a narrowed passageway that can slow the movement of food through the intestine, causing pain or cramps.
Crohn’s disease is an inflammatory bowel disease (IBD), the general name for diseases that cause inflammation and irritation in the intestines. Crohn’s disease can be difficult to diagnose because its symptoms are similar to other intestinal disorders, such as ulcerative colitis and other IBDs, and irritable bowel syndrome. For example, ulcerative colitis and Crohn’s disease both cause abdominal pain and diarrhea.
Crohn’s disease may also be called ileitis or enteritis.
Who gets Crohn’s disease?
Crohn’s disease affects men and women equally and seems to run in some families. People with Crohn’s disease may have a biological relative—most often a brother or sister—with some form of IBD. Crohn’s disease occurs in people of all ages, but it most commonly starts in people between the ages of 13 and 30.1 Men and women who smoke are more likely than nonsmokers to develop Crohn’s disease. People of Jewish heritage have an increased risk of developing Crohn’s disease, and African Americans have a decreased risk.
What causes Crohn’s disease?
The cause of Crohn’s disease is unknown, but researchers believe it is the result of an abnormal reaction by the body’s immune system. Normally, the immune system protects people from infection by identifying and destroying bacteria, viruses, or other potentially harmful foreign substances. Researchers believe that in Crohn’s disease the immune system attacks bacteria, foods, and other substances that are actually harmless or beneficial. During this process, white blood cells accumulate in the lining of the intestines, producing chronic inflammation, which leads to ulcers, or sores, and injury to the intestines.
Researchers have found that high levels of a protein produced by the immune system, called tumor necrosis factor (TNF), are present in people with Crohn’s disease. However, researchers do not know whether increased levels of TNF and abnormal functioning of the immune system are causes or results of Crohn’s disease. Research shows that the inflammation seen in the GI tract of people with Crohn’s disease involves several factors: the genes the person has inherited, the person’s immune system, and the environment.
What are the symptoms of Crohn’s disease?
The most common symptoms of Crohn’s disease are abdominal pain, often in the lower right area, and diarrhea. Rectal bleeding, weight loss, and fever may also occur. Bleeding may be serious and persistent, leading to anemia—a condition in which red blood cells are fewer or smaller than normal, which means less oxygen is carried to the body’s cells. The range and severity of symptoms varies.
How is Crohn’s disease diagnosed?
A doctor will perform a thorough physical exam and schedule a series of tests to diagnose Crohn’s disease.
- Blood tests can be used to look for anemia caused by bleeding. Blood tests may also uncover a high white blood cell count, which is a sign of inflammation or infection somewhere in the body. Blood is drawn at a health care provider’s office or commercial facility and sent to a lab for analysis.
- Stool tests are commonly done to rule out other causes of GI diseases, such as infection. Stool tests can also show if there is bleeding in the intestines. The doctor will give the person a container for catching and storing the stool. The sample is returned to the doctor or a commercial facility and sent to a lab for analysis.
- Flexible sigmoidoscopy and colonoscopy. These tests are used to help diagnose Crohn’s disease and determine how much of the GI tract is affected. Colonoscopy is the most commonly used test to specifically diagnose Crohn’s disease. Colonoscopy is used to view the ileum, rectum, and the entire colon, while flexible sigmoidoscopy is used to view just the lower colon and rectum. For both tests, a health care provider will provide written bowel prep instructions to follow at home before the test. The person may be asked to follow a clear liquid diet for 1 to 3 days before the test. A laxative may be required the night before the test. One or more enemas may be required the night before and about 2 hours before the test.
For either test, the person will lie on a table while the doctor inserts a flexible tube into the anus. A small camera on the tube sends a video image of the intestinal lining to a computer screen. The doctor can see inflammation, bleeding, or ulcers on the colon wall. The doctor may also perform a biopsy by snipping a bit of tissue from the intestinal lining. The person will not feel the biopsy. The doctor will look at the tissue with a microscope to confirm the diagnosis. For a colonoscopy, a light sedative—and possibly pain medication—helps people relax.
Cramping or bloating may occur during the first hour after the test. Driving is not permitted for 24 hours after a colonoscopy to allow the sedative time to wear off. Before the appointment, people should make plans for a ride home. Full recovery is expected by the next day.
- Computerized tomography (CT) scan. CT scans use a combination of x rays and computer technology to create three-dimensional (3-D) images. For a CT scan, the person may be given a solution to drink and an injection of a special dye, called contrast medium. CT scans require the person to lie on a table that slides into a tunnel-shaped device where the x rays are taken. CT scans can be used to help diagnose Crohn’s disease. Children may be given a sedative to help them fall asleep for the test.
- Upper GI series. An upper GI series may be done to look at the small intestine. No eating or drinking is allowed for 8 hours before the procedure, if possible. During the procedure, the person will stand or sit in front of an x-ray machine and drink barium, a chalky liquid. Children may be given a sedative to help them fall asleep for the test. Children who are sedated will lie on a table for the test. Barium coats the small intestine, making signs of Crohn’s disease show up more clearly on x rays.
A person may experience bloating and nausea for a short time after the test. For several days afterward, barium liquid in the GI tract causes stools to be white or light colored. A health care provider will provide specific instructions about eating and drinking after the test.
- Lower GI series. A lower GI series may be done to look at the large intestine. A health care provider may provide written bowel prep instructions to follow at home before the test. The person may be asked to follow a clear liquid diet for 1 to 3 days before the procedure. A laxative or enema may be used before the test. A laxative is medication that loosens stool and increases bowel movements. An enema involves flushing water, laxative, or sometimes a mild soap solution into the anus using a special squirt bottle.
For several days afterward, traces of barium liquid in the large intestine cause stools to be white or light colored. Enemas and repeated bowel movements may cause anal soreness. A health care provider will provide specific instructions about eating and drinking after the test.
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