About Crohn's Disease

Crohn's disease is a chronic (ongoing) disorder that causes inflammation of the digestive or gastrointestinal (GI) tract. Although it can involve any area of the GI tract from the mouth to the anus, it most commonly affects the small intestine and/or colon.
Crohn's and a related disease, ulcerative colitis, are the two main disease categories that belong to a larger group of illnesses called inflammatory bowel disease (IBD).
Because the symptoms of these two illnesses are so similar, it is sometimes difficult to establish the diagnosis definitively. In fact, approximately 10 percent of colitis cases are unable to be pinpointed as either ulcerative colitis or Crohn's disease and are called indeterminate colitis.
Both illnesses do have one strong feature in common. They are marked by an abnormal response by the body's immune system. The immune system is composed of various cells and proteins. Normally, these protect the body from infection. In people with Crohn's disease, however, the immune system reacts inappropriately. Researchers believe that the immune system mistakes microbes, such as bacteria that is normally found in the intestines, for foreign or invading substances, and launches an attack. In the process, the body sends white blood cells into the lining of the intestines, where they produce chronic inflammation. These cells then generate harmful products that ultimately lead to ulcerations and bowel injury. When this happens, the patient experiences the symptoms of IBD.

Although Crohn's disease most commonly affects the end of the small intestine (the ileum) and the beginning of the large intestine (the colon), it may involve any part of the GI tract. In ulcerative colitis, on the other hand, the GI involvement is limited to the colon. In Crohn's disease, all layers of the intestine may be involved, and there can be normal healthy bowel in between patches of diseased bowel. In contrast, ulcerative colitis affects only the superficial layers (the mucosa) of the colon in a more even and continuous distribution, which starts at the level of the anus.
What Causes Crohn's Disease?
Although considerable progress has been made in IBD research, investigators do not yet know what causes this disease. Studies indicate that the inflammation in IBD involves a complex interaction of factors: the genes the person has inherited, the immune system, and something in the environment. Foreign substances (antigens) in the environment may be the direct cause of the inflammation, or they may stimulate the body's defenses to produce an inflammation that continues without control. Researchers believe that once the IBD patient's immune system is "turned on," it does not know how to properly "turn off" at the right time. As a result, inflammation damages the intestine and causes the symptoms of IBD. That is why the main goal of medical therapy is to help patients regulate their immune system better.

Symptoms of Crohn's Disease

By Mayo Clinic staff

Signs and symptoms of Crohn's disease can range from mild to severe and may develop gradually or come on suddenly, without warning. You may also have periods of time when you have no signs or symptoms (remission). When the disease is active, signs and symptoms may include:
Diarrhea. The inflammation that occurs in Crohn's disease causes cells in the affected areas of your intestine to secrete large amounts of water and salt. Because the colon can't completely absorb this excess fluid, you develop diarrhea. Intensified intestinal cramping also can contribute to loose stools. Diarrhea is the most common problem for people with Crohn's.
Abdominal pain and cramping. Inflammation and ulceration may cause the walls of portions of your bowel to swell and eventually thicken with scar tissue. This affects the normal movement of contents through your digestive tract and may lead to pain and cramping. Mild Crohn's disease usually causes slight to moderate intestinal discomfort, but in more-serious cases, the pain may be severe and include nausea and vomiting.

Blood in your stool. Food moving through your digestive tract may cause inflamed tissue to bleed, or your bowel may also bleed on its own. You might notice bright red blood in the toilet bowl or darker blood mixed with your stool. You can also have bleeding you don't see (occult blood).
Ulcers. Crohn's disease can cause small sores on the surface of the intestine that eventually become large ulcers that penetrate deep into — and sometimes through — the intestinal walls. You may also have ulcers in your mouth similar to canker sores.
Reduced appetite and weight loss. Abdominal pain and cramping and the inflammatory reaction in the wall of your bowel can affect both your appetite and your ability to digest and absorb food.

Other signs and symptoms

People with severe Crohn's disease may also experience:

• Fever
• Fatigue
• Arthritis
• Eye inflammation
• Skin disorders
• Inflammation of the liver or bile ducts
• Delayed growth or sexual development, in children

Crohn's disease may lead to one or more of the following complications:

Bowel obstruction. Crohn's disease affects the entire thickness of the intestinal wall. Over time, parts of the bowel can thicken and narrow, which may block the flow of digestive contents through the affected part of your intestine. Some cases require surgery 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) and anus.
Fistulas. Sometimes ulcers can extend completely through the intestinal wall, creating a fistula — an abnormal connection between different parts of your intestine, between your intestine and skin, or between your intestine and another organ, such as the bladder or vagina. When internal fistulas develop, food may bypass areas of the bowel that are necessary for absorption. An external fistula can cause continuous drainage of bowel contents to your skin, and in some cases, a fistula may become infected and form an abscess, a problem that can be life-threatening if left untreated.
Anal fissure. This is a crack, or cleft, in the anus or in the skin around the anus where infections can occur. It's often associated with painful bowel movements.
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. Additionally, anemia is common in people with Crohn's disease.
Other health problems. In addition to inflammation and ulcers in the digestive tract, Crohn's disease can cause problems in other parts of the body, such as arthritis, inflammation of the eyes or skin, clubbing of the fingernails, kidney stones, gallstones and, occasionally, inflammation of the bile ducts. People with long-standing Crohn's disease also may develop osteoporosis, a condition that causes weak, brittle bones.