What is Crohn's disease?
Crohn's disease is one of the main subtypes of inflammatory bowel disease (IBD). Inflammatory bowel disease causes chronic inflammation in the intestinal tract, which leads to a variety of symptoms and can lead to involvement of other organ systems. IBD is a lifelong disease with periods of active disease alternating with periods of disease control (remission). IBD is sometimes confused with but is different than irritable bowel syndrome (IBS). Crohn's disease can involve any part of the intestinal tract from the mouth to the anal area. The most commonly involved areas are the lower part of the small intestine (the ileum) and the colon.
“Skip” lesions can be found in Crohn’s disease -- this means that there can be normal areas in between areas that are inflamed. In addition all layers of the intestinal wall can be involved which may lead to particular complications that are seen only in Crohn’s disease including:
fistula- an abnormal connection between the intestine and other organs
abscess- collection of pus
stricture- an area of narrowing that can lead to intestinal blockage
Because Crohn’s disease usually comes back after surgery, it is generally not curable, however, there are good medical therapies available.
What causes Crohn's disease?
The exact cause of IBD is not known but is related to an overactive immune system. This immune system normally turns on and off to fight harmful substances like bacteria and viruses that pass through intestines. In those who develop IBD, the immune system does not turn off once this initial trigger is gone. This leads to uncontrolled inflammation and attack on normal intestinal cells.
The biggest factor associated with IBD is cigarette smoking. Smokers are more likely to develop Crohn’s disease and have a more aggressive form of disease than non-smokers.
Finally, 10-20% of IBD patients have one or more other family members affected with IBD, either Crohn's disease or ulcerative colitis.
What are the symptoms of Crohn's disease?
The most common symptoms seen in Crohn’s disease are diarrhea, rectal bleeding, urgency to have bowel movements, abdominal cramps and pain, fever, and weight loss. In Crohn’s disease, symptoms can result from complications of the disease. Fistulas can lead to openings in the skin and around the anal region that drain stool and infected material. An abscess can lead to symptoms of severe pain and fever. A stricture can lead to intestinal blockage with symptoms of filling up quickly after meals, nausea and vomiting.
In addition, organs other than the intestinal tract can be involved by the underlying inflammation of IBD. These organs include the eyes (symptoms of red eye or blurred vision), the mouth (symptoms of sores in the mouth), joints (symptoms of joint pain with or without joint swelling and redness), and skin (symptoms of rashes or skin ulcers most commonly involving the lower legs).
How is Crohn's disease diagnosed?
After discussing your symptoms and doing a physical exam, your doctor may order some additional testing. Blood tests can help detect changes such as low red blood cell counts (anemia), high white blood cell counts (indicate inflammation or infection), and low nutrient levels. Stool samples are sometimes checked to rule out intestinal infections, which can lead to similar symptoms as those of IBD.
The most direct way to make a firm diagnosis of IBD involves the use of endoscopy (using a camera to look the intestines), biopsies, or special X-rays. With endoscopy, the lining of the intestinal tract can be directly seen by the doctor performing the procedure and biopsies can be obtained. Typical changes of IBD can be detected by endoscopy and by examining biopsies under a microscope. Barium X-rays (also known as small bowel series or upper GI studies) are also commonly used to diagnose IBD. Patients drink barium (a white fluid), which allows doctors to take X-ray pictures of the small intestine and to look for changes typical of IBD. This test is particularly helpful in evaluating the small intestine, which cannot be fully examined with endoscopes. Another type of X-ray that is sometimes done in patients with IBD is a CAT scan, which is used to look for the presence of an abscess in the abdomen of patients with Crohn’s disease. Capsule endoscopy is a newer test in which a pill is swallowed and then travels through the small intestine taking pictures that are transmitted to a recorder and later viewed on a computer. Recent studies indicate that capsule endoscopy is more sensitive for Crohn’s in the small intestine than x-rays, but the role of capsule endoscopy in Crohn’s disease is not yet identified.
What medications are available for Crohn's?
Crohn’s disease is a chronic illness and often requires long-term treatment with medications. In general there are two main goals of medical therapy for IBD:
Bring active disease under control (into remission)
Keep the disease in remission.
These types of medications are among the most commonly used to treat IBD and include sulfasalazine (Azulfidine®) and mesalamine (Asacol®, Pentasa®, Colazal®). The active component works to reduce inflammation in the intestinal wall. These compounds are prepared differently and based on this release the active ingredient in different parts of the intestinal tract. All the above come as pills taken by mouth but there are also suppository and enema forms of mesalamine that are applied directly into the rectum and used to treat inflammation in the bottom part of the colon.
These medications work well for mild to moderate Crohn’s disease of the colon. They are not as effective for Crohn’s inflammation of the small intestine or for more severe IBD. When effective, they work both to bring active disease under control and to maintain disease in remission. They are generally well tolerated with minimal side effects.
Steroids such as prednisone are commonly used to treat patients with Crohn’s disease. These work as anti-inflammatory agents.The main role of these medications in IBD is to bring the disease into remission. For patients whose disease seems to require repeated or long-term steroid courses, other medical treatment options described below are available and should be considered (see discussion of side effects below). Most commonly these medications are given orally. However, in moderate to severe cases of IBD, patients are brought into the hospital and intravenous steroids are used to bring the disease under control. There are also enema and suppository preparations of steroids available.
There are multiple possible side effects from steroids most of which are more likely to develop with higher doses and longer use. Early side effects can include mood changes, irritability, difficulty sleeping, increased appetite, and increased blood sugar levels. Side effects associated with long-term use include osteoporosis (weakening of the bones), cataracts, acne, development of a fatty hump at the base of the neck, and a rounded/swollen appearance to the face (moon facies). Although there are possible side effects from these types of steroids, they remain an important part of the medical management of inflammatory bowel disease. With appropriate dosing and tapering, most patients tolerate steroids well.
More recently a new steroid preparation named budesonide (Entocort®) has been made available in the United States for treatment of Crohn’s disease. This steroid is specifically designed to treat the intestines with very little of it reaching the bloodstream so there are less side effects when compared to other steroids. This medicine works mostly in treating inflammation in the bottom part of the small intestine (the ileum) and the right part of the colon.
Mercaptopurine and Azathioprine
6-mercaptopurine (Purinethol®) and azathioprine (Imuran®) decrease the activity of the immune system, which then reduces inflammation in the intestines. They used are in Crohn’s disease to bring active disease under control and to keep the disease at bay. They are given orally as pills.
These agents may take a few weeks to months to take their full effect, so other medications such as steroids are sometimes needed on a short-term basis to keep disease under control when starting 6-mercaptopurine or azathioprine. These medications have less long-term side effects than steroids. Approximately 5-10% of patients cannot tolerate these medications due to side effects such as allergic reactions, pancreatitis (inflammation of the pancreas), and abnormal liver tests. Because these medications affect the immune system, patients have a higher risk of developing infections. Therefore, it is recommended that blood counts be monitored on a frequent and regular basis when on these medications.
Methotrexate is another medication that works to decrease the activity of the immune system. It is used in Crohn’s disease both to bring disease into remission and to maintain remission. Methotrexate can be given either as pills or as an injection under the skin or into the muscle, but the studies that have shown that it works in IBD when given as an injection. A vitamin called folate (or folic acid) should be given with methotrexate to decrease some of the side effects. Potential side effects and risks include nausea, vomiting, infections, bone marrow suppression, liver inflammation, and rarely scarring in the lungs. Methotrexate is also known to cause birth defects and therefore should not be used in either males or females who are trying to have a baby.
Infliximab (Remicade®) may be used in moderate to severe Crohn’s disease. It is a medication that is given intravenously and works on reducing intestinal inflammation by blocking a part of the immune system known as TNF (tumor necrosis factor). A single infusion or three short infusions have been shown to bring inflammation into remission and to allow closure of fistulas. The benefit may last approximately two months. However, recent studies have shown that repeated infusions of infliximab over a one-year period are generally well tolerated and can maintain remission. Side effects of this agent include infusion reactions, which are usually mild, and infections. Occasionally the infections are quite serious.
When is surgery indicated for Crohn's?
For Crohn’s disease, indications for surgery include lack of response or intolerance to medications and complications of Crohn’s such as a fistula, an abscess, or a stricture. Up to 70% of patients with Crohn’s disease require surgery at some point in the course of their disease. The risk of having Crohn’s disease return after surgery is approximately 70-85% within 10-15 years after surgery. There is growing evidence that medications can be used to decrease the risk of Crohn’s returning following surgery.