What is Crohn’s disease?
Crohn’s disease is a type of inflammatory bowel disease (IBD). It causes swelling of the tissues (inflammation) in your digestive tract, which can lead to abdominal pain, severe diarrhea, fatigue, weight loss and malnutrition. Inflammation caused by Crohn’s disease can involve different areas of the digestive tract in different people, most commonly the small intestine. This inflammation often spreads into the deeper layers of the bowel.
Crohn’s disease can be both painful and debilitating, and sometimes may lead to life-threatening complications. There’s no known cure for Crohn’s disease, but therapies can greatly reduce its signs and symptoms and even bring about long-term remission and healing of inflammation. With treatment, many people with Crohn’s disease are able to function well.
Crohn’s disease is a type of inflammatory bowel disease (IBD). It causes swelling of the tissues (inflammation) in your digestive tract, which can lead to abdominal pain, severe diarrhea, fatigue, weight loss and malnutrition. Inflammation caused by Crohn’s disease can involve different areas of the digestive tract in different people, most commonly the small intestine. This inflammation often spreads into the deeper layers of the bowel. Crohn’s disease can be both painful and debilitating, and sometimes may lead to life-threatening complications. There’s no known cure for Crohn’s disease, but therapies can greatly reduce its signs and symptoms and even bring about long-term remission and healing of inflammation. With treatment, many people with Crohn’s disease are able to function well.
The exact cause of Crohn’s disease remains unknown. Previously, diet and stress were suspected, but now doctors know that these factors may aggravate, but don’t cause, Crohn’s disease. Several factors likely play a role in its development.
- Immune system. It’s possible that a virus or bacterium may trigger Crohn’s disease; however, scientists have yet to identify such a trigger. When your immune system tries to fight off an invading microorganism or environmental triggers, an atypical immune response causes the immune system to attack the cells in the digestive tract, too.
- Heredity. Crohn’s disease is more common in people who have family members with the disease, so genes may play a role in making people more likely to have it. However, most people with Crohn’s disease do not have a family history of the disease.
Risk factors for Crohn’s disease may include:
- Age. Crohn’s disease can occur at any age, but you’re likely to develop the condition when you’re young. Most people who develop Crohn’s disease are diagnosed before they’re around 30 years old.
- Ethnicity. Although Crohn’s disease can affect any ethnic group, whites have the highest risk, especially people of Eastern European (Ashkenazi) Jewish descent. However, the incidence of Crohn’s disease is increasing among Black people who live in North America and the United Kingdom. Crohn’s disease is also being increasingly seen in the Middle Eastern population and among migrants to the United States.
- Family history. You’re at higher risk if you have a first-degree relative, such as a parent, sibling or child, with the disease. As many as 1 in 5 people with Crohn’s disease has a family member with the disease.
- Cigarette smoking. Cigarette smoking is the most important controllable risk factor for developing Crohn’s disease. Smoking also leads to more-severe disease and a greater risk of having surgery. If you smoke, it’s important to stop.
- Nonsteroidal anti-inflammatory medications. These include ibuprofen (Advil, Motrin IB, others), naproxen sodium (Aleve), diclofenac sodium and others. While they do not cause Crohn’s disease, they can lead to inflammation of the bowel that makes Crohn’s disease worse.
ComplicationsCrohn’s disease may lead to one or more of the following complications:
- Bowel obstruction. Crohn’s disease can affect the entire thickness of the intestinal wall. Over time, parts of the bowel can scar and narrow, which may block the flow of digestive contents, often known as a stricture. You may require surgery to widen the stricture or sometimes to remove the diseased portion of your bowel.
- Ulcers. Chronic inflammation can lead to open sores (ulcers) anywhere in your digestive tract, including your mouth and anus, and in the genital area (perineum).
- Fistulas. Sometimes ulcers can extend completely through the intestinal wall, creating a fistula — an abnormal connection between different body parts. Fistulas can develop between your intestine and your skin, or between your intestine and another organ. Fistulas near or around the anal area (perianal) are the most common kind. When fistulas develop inside the abdomen, it may lead to diseases and abscesses, which are collections of pus. These can be life-threatening if not treated. Fistulas may form between loops of bowel, in the bladder or vagina, or through the skin, causing continuous drainage of bowel contents to your skin.
- Anal fissure. This is a small tear in the tissue that lines the anus or in the skin around the anus where diseases can occur. It’s often associated with painful bowel movements and may lead to a perianal fistula.
- Malnutrition. Diarrhea, abdominal pain and cramping may make it difficult for you to eat or for your intestine to absorb enough nutrients to keep you nourished. It’s also common to develop anemia due to low iron or vitamin B-12 caused by the disease.
- Colon cancer. Having Crohn’s disease that affects your colon increases your risk of colon cancer. General colon cancer screening guidelines for people without Crohn’s disease call for a colonoscopy at least every 10 years beginning at age 45. In people with Crohn’s disease affecting a large part of the colon, a colonoscopy to screen for colon cancer is recommended about 8 years after disease onset and generally is performed every 1 to 2 years afterward. Ask your doctor whether you need to have this test done sooner and more frequently.
- Skin disorders. Many people with Crohn’s disease may also develop a condition called hidradenitis suppurativa. This skin disorder involves deep nodules, tunnels and abscesses in the armpits, groin, under the breasts, and in the perianal or genital area.
- Other health problems. Crohn’s disease can also cause problems in other parts of the body. Among these problems are low iron (anemia), osteoporosis, arthritis, and gallbladder or liver disease.
- Medication risks. Certain Crohn’s disease drugs that act by blocking functions of the immune system are associated with a small risk of developing cancers such as lymphoma and skin cancers. They also increase the risk of diseases. Corticosteroids can be associated with a risk of osteoporosis, bone fractures, cataracts, glaucoma, diabetes and high blood pressure, among other conditions. Work with your doctor to determine risks and benefits of medications.
- Blood clots. Crohn’s disease increases the risk of blood clots in veins and arteries.
DiagnosisYour doctor will likely diagnose Crohn’s disease only after ruling out other possible causes for your signs and symptoms. There is no single test to diagnose Crohn’s disease. Your doctor will likely use a combination of tests to help confirm a diagnosis of Crohn’s disease, including:
- Blood tests. Your doctor may suggest blood tests to check for anemia — a condition in which there aren’t enough red blood cells to carry adequate oxygen to your tissues — or to check for signs of disease. Your doctor may also perform other tests to check for levels of inflammation, liver function, or the presence of inactive diseases, such as tuberculosis. Your blood may also be screened for the presence of immunity against diseases.
- Stool studies. You may need to provide a stool sample so that your doctor can test for hidden (occult) blood or organisms, such as disease-causing bacteria or, rarely, parasites in your stool.
- Colonoscopy. This test allows your doctor to view your entire colon and the very end of your ileum (terminal ileum) using a thin, flexible, lighted tube with a camera at the end. During the procedure, your doctor can also take small samples of tissue (biopsy) for laboratory analysis, which may help to make a diagnosis. Clusters of inflammatory cells called granulomas may help suggest a diagnosis of Crohn’s.
- Computerized tomography (CT). You may have a CT scan — a special X-ray technique that provides more detail than a standard X-ray does. This test looks at the entire bowel as well as at tissues outside the bowel. CT enterography is a special CT scan that involves drinking an oral contrast material and getting intravenous contrast images of the intestines. This test provides better images of the small bowel and has replaced barium X-rays in many medical centers.
- Magnetic resonance imaging (MRI). An MRI scanner uses a magnetic field and radio waves to create detailed images of organs and tissues. MRI is particularly useful for evaluating a fistula around the anal area (pelvic MRI) or the small intestine (MR enterography). Sometimes an MR enterography can be performed to check for disease status or progression. This test may be used instead of CT enterography to reduce the risk of radiation, especially in younger people.
- Capsule endoscopy. For this test, you swallow a capsule that has a camera in it. The camera takes pictures of your small intestine and sends them to a recorder you wear on your belt. The images are then downloaded to a computer, displayed on a monitor and checked for signs of Crohn’s disease. The camera exits your body painlessly in your stool. You may still need endoscopy with biopsy to confirm the diagnosis of Crohn’s disease. Capsule endoscopy should not be performed if there is a suspected stricture or blockage (obstruction) in the bowel.
- Balloon-assisted enteroscopy. For this test, a scope is used along with a device called an overtube. This enables the doctor to look further into the small bowel where standard endoscopes don’t reach. This technique is useful when capsule endoscopy shows abnormalities but the diagnosis is still in question.