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Crohn's disease is a form of inflammatory bowel disease (IBD). It usually affects the intestines, but may occur anywhere from the mouth to the end of the rectum (anus).

See also: Ulcerative colitis

Inflammatory bowel disease - Crohn's disease; Regional enteritis; Ileitis; Granulomatous ileocolitis; IBD- Crohn's disease

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 normal body tissue and foreign substances. The result is an overactive immune response that leads to chronic inflammation. This is called an autoimmune disorder.

People with Crohn's disease have ongoing (chronic) inflammation of the gastrointestinal tract. Crohn's disease 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.

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 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
• Loss of appetite
• Pain with passing stool (tenesmus)
• Persistent, watery diarrhea
• Unintentional weight loss

Other symptoms may include:

• Constipation
• Eye inflammation
• Fistulas (usually around the rectal area, may cause draining of pus, mucus, or stools)
• Joint pain
• Liver inflammation
• Mouth ulcers
• Rectal bleeding and bloody stools
• Skin rash
• Swollen gums

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, including capsule endoscopy
• Magnetic resonance imaging (MRI) of the abdomen
• Sigmoidoscopy
• Enteroscopy
• 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

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, such as thinning of the bones
• 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 deficiency (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

Lichtenstein GR, Hanauer SB, Sandborn WJ; Practice Parameters Committee ofAmerican Collegeof Gastroenterology. Management of Crohn's disease in adults. Am J Gastroenterol. 2009 Feb;104(2):465-83. Epub 2009 Jan 6.

Fry RD, Mahmoud N, Maron DJ, Ross HM, Rombeau J. Colon and rectum. In: Townsend CM, Beauchamp RD, Evers BM, Mattox KL, eds. Sabiston Textbook of Surgery. 18th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 50.

Rutgeerts P, Vermeire S, Van Assche G. Biological therapies for inflammatory bowel diseases. Gastroenterology. 2009 Apr;136(4):1182-97. Epub 2009 Feb 26.