Crohn's disease is a form of inflammatory bowel disease (IBD), which involves ongoing (chronic) inflammation of the gastrointestinal tract. Crohn's-related inflammation usually affects the intestines, but may occur anywhere from the mouth to the anus (the end of the rectum).

See also: Ulcerative colitis

While the exact chain of events that lead to Crohn's disease is unknown, the condition is linked to a problem with the body's immune system response. Normally the immune system helps protect the body from harmful substances. But in patients with Crohn's disease and other types of inflammatory bowel disease (IBD), the immune system can't tell the difference between good substances and foreign invaders. The result is an overactive immune response that leads to chronic inflammation. This is called an autoimmune disorder.

There are five different types of Crohn's disease:

• Ileocolitis is the most common form. It affects the lowest part of the small intestine (ileum) and the large intestine (colon).
• Ileitis affects the ileum.
• Gastroduodenal Crohn's disease causes inflammation in the stomach and first part of the small intestine, called the duodenum.
• Jejunoileitis causes spotty patches of inflammation in the top half of the small intestine (jejunum).
• Crohn's (granulomatous) colitis only affects the large intestine.

A person's genes and environmental factors seem to play a role in the development of Crohn's disease.

The inflammation related to Crohn's disease frequently occurs at the end of the small intestine that joins the large intestine, but it may occur in any area of the digestive tract. There can be healthy patches of tissue in between diseases areas. The ongoing inflammation causes the intestinal wall to become thick.

The disease may occur at any age, but it usually occurs in persons between ages 15 and 35. Risk factors include a family history of Crohn's disease, Jewish ancestry, and smoking.

Symptoms depend on what part of the gastrointestinal tract is affected. Symptoms range from mild to severe, and can come and go with periods of flare-ups.

The main symptoms of Crohn's disease are:

• Crampy abdominal (belly area) pain
• Persistent, watery diarrhea
• Fever
• Fatigue

Other symptoms may include:

• Rectal bleeding and bloody stools
• Loss of appetite
• Unintentional weight loss
• Constipation
• Abdominal fullness and gas
• Gastrointestinal bleeding
• Foul-smelling stools
• Tenesmus (pain with passing stool)
• Fistulas (usually around the rectal area, may cause draining of pus, mucus, or stools)
• Liver inflammation
• Joint pain
• Skin rash
• Swollen gums
• Eye inflammation
• Kidney stones
• Clotting problems (deep vein thrombosis)

A physical examination may reveal an abdominal mass or tenderness, skin rash, swollen joints or mouth ulcers. The doctor may use a stethoscope to listen to the belly area. Abdominal sounds (borborygmus, a gurgling or splashing sound heard over the intestine) may be heard.

Tests to diagnose Crohn's disease include:

• Endoscopy
• Colonoscopy
• Sigmoidoscopy with small bowel biopsy
• Small bowel x-ray series
• Barium enema
• Upper GI series
• Stool guaiac test

A stool culture may be done to rule out other possible causes of the symptoms.

This disease may also alter the results of the following tests:

• Fecal fat
• Liver function tests
• Albumin

Medicines that may be prescribed include:

• Aminosalicylates (5-ASAs) are medicines that help control mild to moderate inflammation. Some forms of the drug are taken by mouth; others must be given rectally.
• Corticosteroids (prednisone and methylprednisolone) are used to treat moderate to severe Crohn's disease. They may be taken by mouth or inserted into the rectum.
• Immunomodulators such as azathioprine or 6-mercaptopurine help reduce the need for corticosteroids and can help heal some fistulas.
• Antibiotics may be prescribed for abscesses or fistulas.
• Biologic therapy is used to treat patients with severe Crohn's disease that does not respond to any other types of medication. Infliximab (Remicade) and adalimumab (Humira) are approved for Crohn's disease. They belong to a class of drugs called monoclonal antibodies, which help block an immune system chemical that promotes inflammation. Infliximab is also approved for patients with fistulous disease.

If medicines do not work, a type of surgery called bowel resection may be needed to remove a damaged or diseased part of the intestine or to drain an abscess. A procedure called anastomosis is done to connect the remaining two ends of the bowel. According to the Crohn's and Colitis Foundation of America, two-thirds to three-quarters of patients with Crohn's disease will need bowel surgery at some time. However, unlike ulcerative colitis, surgical removal of a diseased portion of the intestine does not cure the condition.

Some persons with Crohn's disease may need surgery to remove the entire large intestine (colon) with or without the rectum.

Removal of the entire large intestine is called a colectomy. The small intestine is connected to the rectum.

Removal of both the colon and rectum is called a proctocolectomy. Since the body still needs a way to move stool and waste through the body after an proctocolectomy, a new pathway must be created. The surgeon will attach the end of the small intestine to an opening in the abdominal wall. A pouch is attached to the opening and worn outside the body. Waste products empty into the pouch. You must empty the pouch several times a day. The pouch can be worn discreetly under clothing, so no one will know you have it.

No specific diet has been shown to improve or worsen the bowel inflammation in Crohn's disease. However, eating a healthy amount of calories, vitamins, and protein is important to avoid malnutrition and weight loss. Foods that worsen diarrhea should be avoided. Specific food problems may vary from person to person.

People who have blockage of the intestines may need to avoid raw fruits and vegetables. Those who have difficulty digesting lactose (milk sugar) need to avoid milk products.

The Crohn's and Colitis Foundation of America offers support groups throughout the United States. See http://www.ccfa.org/chapters/

There is no cure for Crohn's disease. The condition is marked by periods of improvement followed by flare ups of symptoms.

You have a higher risk for small bowel and colon cancer if you have Crohn's disease. Dietary and lifestyle modifications are important. Some evidence suggests that low-fat and high-fiber diets may reduce your risk of colon cancer. Ask your doctor if this may be best for you.

• Fistulas in the following areas:
  • Bladder
  • Vagina
  • Skin
• Bowel obstructions
• Abscess
• Nutritional deficiencies (particularly vitamin B12 deficiency)
• Complications of corticosteroid therapy
• Inflammation of the joints
• Erythema nodosum
• Pyoderma gangrenosum
• Lesions in the eye
• Impaired growth and sexual development in children

Call for an appointment with your health care provider if:

• You have symptoms of Crohn's disease
• You are already diagnosed with Crohn's disease and your symptoms get worse or do not improve with treatment
• You already diagnosed with Crohn's disease and you develop new symptoms

US Food and Drug Administration. FDA Approves New Treatment For Crohn's Disease. Rockville, MD: National Press Office; February 27, 2007: Report P07-30.

Sandborn WJ, Hanauer SB, Rutgeerts PJ, et al. Adalimumab for Maintenance Treatment of Crohn's Disease: Results of the CLASSIC II Trial. Gut. 2007 Feb 13 [Epub ahead of print].

Hawk ET, Levin B. Colorectal cancer prevention. J Clin Oncol. 2005;23:378-388.