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 end of the rectum (anus).

See also: Ulcerative colitis

While the exact cause of 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, but with Crohn's disease 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 body may be overreacting to normal bacteria in the intestines.

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 between diseased areas. The ongoing inflammation causes the intestinal wall to become thick.

The disease may occur at any age, but it usually occurs in people between ages 15 - 35. Risk factors include:

• Family history of Crohn's disease
• Jewish ancestry
• 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
• Fever
• Fatigue
• Persistent, watery diarrhea

Other symptoms may include:

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

A physical examination may reveal an abdominal mass or tenderness, skin rash, swollen joints, or mouth ulcers. Tests to diagnose Crohn's disease include:

• Barium enema
• Colonoscopy
• Computed tomography (CT scan) of the abdomen
• Endoscopy
• Magnetic resonance imaging (MRI) of the abdomen
• Sigmoidoscopy with enteroscopy
• Small bowel x-ray series
• Upper GI series

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:

• Albumin
• C-reactive protein
• Erythrocyte sedimentation rate
• Fecal fat
• Hemoglobin
• Liver function tests
• White blood cell count

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. Other related drugs are being studied.

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, surgically removing the diseased portion of the intestine does not cure the condition.

Patients who have Crohn's disease that does not respond to medications may need surgery, especially when there are complications such as:

• Bleeding (hemorrhage)
• Fistulas
• Infections (abscesses)
• Narrowing (strictures)

Some patients may need surgery to remove the entire large intestine (colon), with or without the rectum.

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. Avoid foods that worsen diarrhea. Specific food problems may vary from person to person.

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

It is very important to stay on medications long-term to try to keep the disease symptoms from returning. If you stop or change your medications for any reason, let your doctor know right away.

You have a higher risk for small bowel and colon cancer if you have Crohn's disease.

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

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 are already diagnosed with Crohn's disease and you develop new symptoms

U.S. 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;56:1232-1239.

Gardiner KR, Dasari BV. Operative management of small bowel Crohn's disease. Surg Clin North Am. 2007;87(3):587-610.

Graham L. AGA Reviews the use of corticosteroids, immunomodulators, and infliximab in IBD. Am Fam Physician. 2007;75(3):410-412.