Crohn’s disease is a chronic inflammatory disorder that primarily affects the small intestine, but it also can affect any segment of the digestive tract, including the colon, anus, mouth, and stomach. Crohn’s disease can even affect the skin. About 700,000 people in the United States have Crohn’s disease.
Causes of Crohn’s disease
Despite extensive research, the cause of Crohn’s disease is poorly understood. Three factors likely play a role. Genetics is one of them: Certain people inherit a susceptibility to the disease. The second factor is environmental: A stimulus (perhaps a virus or bacterium) triggers the disease by causing the immune system to mount an attack against the digestive tract. Once the immune system gets turned on, it doesn’t turn off properly. The third factor is race and ethnicity: Whites (particularly American Jews of European descent), followed by African-Americans, are more likely to get Crohn’s than are Hispanics and Asians.
Symptoms of Crohn’s disease
Most often, Crohn’s disease causes chronic inflammation of the small intestine. The inner lining of the small intestine becomes swollen and may develop erosions and ulcerations. These inflammatory changes usually result in abdominal pain and bloody diarrhea.
The chronic inflammation can also lead to complications such as bowel perforation, peritonitis, abscesses, fistulas, and strictures. Symptoms of Crohn’s disease usually begin in the teen or young adult years. Once you have the disease you will have it for life. However, you will have symptom-free periods (remissions) that can last for years. A reappearance of symptoms is called a flare-up.
Diagnosis of Crohn’s disease
The tests used to diagnose Crohn’s disease depend on where your doctor thinks the inflammation is occurring. An upper gastrointestinal series is the best test for Crohn’s disease of the small intestine. Increasingly, capsule endoscopy is being used for diagnosis, although there is a risk that the capsule could get stuck in the digestive tract of people with Crohn’s disease who have strictures (which are common). Sometimes before a capsule endoscopy, doctors will prescribe a “patency capsule,” which can detect the presence of strictures and (if it gets stuck) dissolve within 40 to 80 hours.
Colonoscopy or sigmoidoscopy may be used to detect Crohn’s disease of the large intestine. If these tests aren’t possible because of narrowing of the rectum or colon, a barium enema may be performed instead. If a fistula is suspected, the doctor may choose a more watery contrast dye called Gastrografin instead of barium. Genetic tests and blood tests are currently in development to detect Crohn’s disease, but they are not yet sensitive or specific enough to be useful.
Treatment of Crohn’s disease
No drug or surgical procedure can cure Crohn’s disease. Treatment is aimed at preventing and treating flare-ups and complications.
Because eating can irritate an inflamed bowel, severe flare-ups usually require hospital treatment with intravenous nutrition and fluids to allow the bowel to rest. You will also be given intravenous corticosteroids like methylprednisolone and mesalamine capsules (Pentasa) or sulfasalazine (Azulfidine) tablets to reduce inflammation. Pentasa can be used to treat disease in both the small and the large intestine. If the disease is present only in the colon, Azulfidine can be used.
If the disease responds to these treatments, you can switch from intravenous to oral corticosteroids such as prednisone or budesonide (Entocort EC). Eventually, you will likely be weaned off corticosteroids, but you will still take mesalamine or sulfasalazine. When Crohn’s disease is limited to the far end of the colon and the rectum, you may receive hydrocortisone (Colocort) or mesalamine (Rowasa) enemas in addition to the treatments just mentioned.
If Crohn’s disease does not improve with corticosteroids and mesalamine or sulfasalazine, immunosuppressive medications may be tried. The most commonly used are mercaptopurine(Purinethol) and azathioprine (Imuran), both given orally.
The immunosuppressant infliximab (Remicade) is especially effective when fistulas are present. It is injected about once every two months and is usually tried only when you do not respond to conventional therapy. However, serious complications have been reported in people using Remicade, a drug that comes with an increased risk of infections and hypersensitivity reactions. In addition, because Remicade can allow latent (silent) tuberculosis to develop into full-blown tuberculosis, you should receive a tuberculin skin test before beginning therapy.
Adalimumab (Humira) is also available for the treatment of moderately to severely active Crohn’s disease. Humira is also an immunosuppressant, but it does not require intravenous injection—the drug is packaged in an injection pen that can be self- administered once every two weeks. Humira is intended for people who cannot tolerate Remicade or who become resistant to it over time. Like Remicade, Humira carries a risk of infection, and it may increase your risk of lymphoma and leukemia.
Two newer immunosuppressants to treat Crohn’s disease, natalizumab (Tysabri) and certolizumab pegol (Cimzia), are similar to Remicade and Humira. They are administered by injection at your doctor’s office. The first three injections are given two weeks apart; if the medication appears to be helping, you’ll receive additional doses every four weeks. Tysabri is a multiple sclerosis drug that has a risk of severe side