Crohn disease is an inflammatory bowel disease where chronic inflammation typically involves the lower part of the small intestine, the large intestine, or both and may affect any part of the digestive tract.
Although the exact cause is unknown, an improperly triggered immune system may result in Crohn disease.
Typical symptoms include chronic diarrhea (which sometimes is bloody), crampy abdominal pain, fever, loss of appetite, and weight loss.
The diagnosis is based on a colonoscopy, video capsule endoscopy, and imaging tests such as barium x-rays, computed tomography, or magnetic resonance imaging.
There is no cure for Crohn disease.
Treatment is aimed at relieving symptoms and reducing inflammation, and some people require surgery.
(See also Overview of Inflammatory Bowel Disease (IBD).)
In the past few decades, Crohn disease has become more common worldwide. However, it is most common among people of Northern European and Anglo-Saxon descent. It occurs about equally in both sexes, often runs in families, and seems to be more common among people of Ashkenazi Jewish ancestry. Most people develop Crohn disease before age 30, usually between the ages of 14 and 24. A few people have their first attack between the ages of 50 and 70.
Most commonly, Crohn disease occurs in the last portion of the small intestine (ileum) and in the large intestine, but it can occur in any part of the digestive tract, from the mouth to the anus and even in the skin around the anus. Inflammation of the ileum is called ileitis. When Crohn disease affects the colon, it is called Crohn colitis. Crohn disease affects
The small intestine alone (30% of people)
The large intestine alone (30% of people)
Both the small intestine and the large intestine (40% of people)
The rectum is usually not affected, unlike in ulcerative colitis, in which the rectum is always involved. However, infections and other complications around the anus are not unusual. The disease may affect some segments of the intestinal tract while leaving normal segments (called skip areas) between the affected areas. Where Crohn disease is active, the full thickness of the bowel is usually involved.
Locating the Small and Large Intestines
The cause of Crohn disease is not known for certain, but many researchers believe that a dysfunction of the immune system causes the intestine to overreact to an environmental, dietary, or infectious agent. Certain people may have a hereditary predisposition to this immune system dysfunction. Cigarette smoking seems to contribute to both the development and the periodic flare-ups (bouts or attacks) of Crohn disease. Oral contraceptives may increase the risk of Crohn disease.
For unclear reasons, people who have a higher socioeconomic status may have an increased risk of Crohn disease.
Several reports suggest that people who were breastfed as infants may be protected from developing inflammatory bowel disease, such as Crohn disease or ulcerative colitis.
Symptoms of Crohn Disease
The most common symptoms of Crohn disease are
Crampy abdominal pain
Chronic diarrhea (which sometimes is bloody when the large intestine is severely affected)
Fever
Loss of appetite
Weight loss
Symptoms of Crohn disease may continue for days or weeks and may resolve without treatment. Complete and permanent recovery after a single attack is extremely rare. Crohn disease almost always flares up at irregular intervals throughout a person's life. Flare-ups can be mild or severe, brief or prolonged. Severe flare-ups can lead to intense, constant pain, fever, and dehydration.
Why the symptoms come and go and what triggers new flare-ups or determines their severity is not known. Recurring inflammation tends to appear in the same area of the intestine. It also may appear in areas near where a diseased segment has been removed surgically.
In children, abdominal pain and diarrhea often are not the main symptoms and may not appear at all. Instead, the main symptoms may be slow growth, joint inflammation (arthritis), fever, or weakness and fatigue resulting from anemia.
Complications of Crohn disease
Complications of Crohn disease include
Intestinal blockage (obstruction)
Perforation (rupture) of the bowel
Abscesses (pus-filled pockets of infection) in the abdomen
Fistulas (abnormal connecting channels between the intestine and skin or other organs)
Anal fissures (tears in the skin of the anus) and anal abscesses
Colon cancer (cancer of the large intestine)
Toxic colitis is a rare complication that can happen when Crohn disease affects the large intestine (colon). The large intestine stops its normal contractions and dilates, sometimes leading to peritonitis. People may need surgery.
Scarring due to chronic inflammation can cause intestinal blockage. Deep ulcers that penetrate through the bowel wall can create abscesses, open fistulas, or perforations. Fistulas may connect 2 different parts of the intestine. Fistulas may also connect the intestine and bladder or the intestine and the skin surface, especially around the anus. Although fistulas from the small intestine are common, wide-open holes (perforations) are rare. Fissures in the skin of the anus are common.
When the large intestine is affected extensively by Crohn disease, rectal bleeding commonly occurs. After many years, the risk of colon cancer (cancer of the large intestine) is increased in people who have Crohn colitis. About one third of people who develop Crohn disease have problems around the anus, especially fistulas and fissures in the lining of the mucus membrane of the anus.
Crohn disease may lead to complications in other parts of the body. These complications include
Inadequate absorption of nutrients (malabsorption)
Deposits of the protein amyloid in several organs (amyloidosis)
When Crohn disease causes a flare-up of gastrointestinal symptoms, the person may also have the following:
Inflammation of the joints (arthritis)
Inflammation of the whites of the eyes (episcleritis)
Mouth sores (aphthous stomatitis)
Inflamed skin nodules on the arms and legs (erythema nodosum)
Even when Crohn disease is not causing a flare-up of gastrointestinal symptoms, the person still may have the following, entirely without relation to the bowel disease:
Inflammation of the spine (ankylosing spondylitis)
Inflammation of the pelvic joints (sacroiliitis)
Inflammation inside the eye (uveitis)
Inflammation of the bile ducts (primary sclerosing cholangitis)
Dusky purple skin sores that may contain pus (pyoderma gangrenosum)
Diagnosis of Crohn Disease
Blood and stool tests
Imaging tests
Colonoscopy
A doctor may suspect Crohn disease in a person with recurring crampy abdominal pain and diarrhea, particularly if the person has a family history of Crohn disease or a history of problems around the anus. Other clues to the diagnosis may include inflammation in the joints, eyes, or skin or stunted growth in a child. The doctor may feel a lump or fullness in the lower part of the abdomen, most often on the right side.
Blood and stool tests
No laboratory test specifically identifies Crohn disease, but blood tests may show anemia, abnormally high numbers of white blood cells, low levels of the protein albumin, and other indications of inflammation, such as an elevated erythrocyte sedimentation rate or level of C-reactive protein. A doctor may also do liver tests.
If diarrhea is present, a doctor may collect stool samples to rule out certain intestinal infections.
Imaging tests
People who have severe abdominal pain and tenderness often have a computed tomography (CT) scan or magnetic resonance imaging (MRI) of their abdomen. CT or MRI may show a blockage, abscesses or fistulas, and other possible causes of inflammation of the abdomen (such as appendicitis).
People who have had symptoms that recur over a period of time may have x-rays taken of the stomach and small intestine after drinking liquid barium (called an upper gastrointestinal [GI] series with small-bowel follow-through) or have x-rays taken after receiving barium as an enema (called a barium enema). Newer approaches include CT enterography or magnetic resonance enterography. Another way in which the small intestine can be evaluated is with video capsule endoscopy.
Colonoscopy
People who have little pain and mostly diarrhea undergo a colonoscopy (an examination of the large intestine with a flexible viewing tube) and a biopsy (removal of a tissue specimen for microscopic examination). If Crohn disease is limited to the small intestine, colonoscopy will not detect the disease unless the colonoscope is advanced all the way through the colon and into the last part of the small intestine where the inflammation most often resides.
Treatment of Crohn Disease
Antidiarrheal medications
Aminosalicylates
Corticosteroids
Immunomodulating medications
Biologic agents
Small-molecule agents
Antibiotics
Dietary regimens
Sometimes surgery
Many treatments of Crohn disease help reduce inflammation and relieve symptoms.
General management
Routine health maintenance measures, particularly vaccinations and cancer screening, are important.
Antidiarrheal medications
Aminosalicylates
Corticosteroids
Corticosteroids: Uses and Side Effects). Usually, high doses are taken initially to relieve major inflammation and symptoms caused by sudden flare-ups. The dose is then reduced and the medication is discontinued as soon as possible.
If the disease becomes severe, the person is hospitalized and corticosteroids are given by vein (intravenously).
Immunomodulating medications
are medications that decrease the actions of the immune system. They are effective for people with Crohn disease who do not respond to other medications and are especially effective for maintaining long periods of remission (periods of no symptoms). They significantly improve the person's overall condition, decrease the need for corticosteroids, and often heal fistulas. However, these medications may not produce benefits for 1 to 3 months and may have potentially serious side effects.
pancreatitis), and sometimes liver problems. People who take these medications have an increased risk of developing lymphoma, a cancer of white blood cells, and some types of skin cancer (monitored by routine skin examinations).
contraceptive method (birth control) such as an intrauterine device (IUD), a contraceptive implant, or an oral contraceptive
is given by injection in high doses. This medication may help heal fistulas caused by Crohn disease, but it cannot safely be used long term because of side effects such as kidney problems, infections, and seizures.
Biologic agents
Certolizumab
progressive multifocal leukoencephalopathy
is another kind of biologic agent. The first dose is given by vein and then by injections under the skin every 8 weeks. Side effects include injection-site reactions (pain, redness, swelling), cold-like symptoms, chills, and headache.
is used to treat moderate to severe Crohn disease. The most common side effects are headaches, fatigue, common cold, and rare candida (yeast) infections. Severe allergic reactions are very rare, but skin reactions at the site of the injection may occur.
is a Janus kinase inhibitor taken orally that is used to treat Crohn disease and ulcerative colitis. The most common side effects of this medication are acne, folliculitis (infections at the hair follicles), upper respiratory tract infection, hypersensitivity reactions, nausea, and abdominal pain. It increases risk for developing serious infection, heart attack, stroke, venous thrombosis (blood clot), pulmonary embolism, and arterial thrombosis.
Biosimilars are biologic medications that are very similar to a reference biologic product. Some biosimilars are commercially available.
Broad-spectrum antibiotics and probiotics
Dietary regimens
Although some people claim that certain diets have helped improve their Crohn disease, diets have not been shown to be effective in clinical trials. Nutritional therapy may help children grow more than they might otherwise, especially when given at nighttime by tube feeding. Occasionally, concentrated nutrients are given intravenously to compensate for the poor absorption of nutrients that is typical of Crohn disease.
Surgery
Most people with Crohn disease require surgery at some point during their illness. Surgery is needed when the intestine is obstructed or when abscesses or fistulas do not heal. An operation to remove diseased sections of the intestine may relieve symptoms indefinitely, but it does not cure the disease. Crohn disease tends to recur where the remaining intestine is rejoined, although several medication therapies initiated after surgery reduce this tendency.
A second operation is ultimately needed in nearly half of the people. Consequently, surgery is done only if specific complications or the failure of medication treatment makes it necessary. Still, most people who have undergone surgery consider their quality of life to be better than it was before the operation.
Because smoking increases the risk of recurrence, especially in women, doctors encourage people to quit smoking.
General management
People who have severe disease may be hospitalized and given intravenous fluids to restore and maintain body fluids (hydration). Some people who have heavy rectal bleeding may require blood transfusions. People who have more chronic anemia may need iron supplements taken by mouth or given intravenously.
Severity of symptoms
For people who have mild to moderate symptoms,
For people who have moderate to severe symptoms,
If people have a blockage, doctors do nasogastric suction and give fluids by vein. In nasogastric suction, a tube is passed through the nose into the stomach or small intestine, and suction is applied to the tube to relieve abdominal swelling (distention).
For people whose symptoms developed suddenly or who have an abscess, fluids and antibiotics are given by vein in a hospital. Doctors drain the abscess surgically or by inserting a needle under the skin and drawing out the fluid.
Fistulas
People with fistulas around the anus (perianal fistulasbiologic agents
Maintenance regimens
During remission, doctors monitor people's symptoms and do blood tests. Routine x-rays or colonoscopy does not need to be done (except in people who have had Crohn disease for 7 or 8 years or longer).
Prognosis for Crohn Disease
Crohn disease has no known cure and is characterized by intermittent flare-ups of symptoms. Flare-ups may be mild or severe, few or frequent. With proper treatment, most people continue to lead productive lives. However, about 10% of people with Crohn disease are disabled by the disease and its complications.
More Information
The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.
Crohn's and Colitis Foundation of America: General information on Crohn disease and ulcerative colitis, including access to support services
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)—Crohn's Disease: General information on Crohn disease, including information about research and clinical trials
