Crohn’s disease : Overview, Causes, & Risk Factors

Alternate Names : Inflammatory bowel disease – Crohn’s disease, Regional enteritis, Ileitis, Granulomatous ileocolitis, IBD- Crohn’s disease

Definition

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

Overview, Causes, & Risk Factors

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

Pictures & Images

Digestive system

The esophagus, stomach, large and small intestine, aided by the liver, gallbladder and pancreas convert the nutritive components of food into energy and break down the non-nutritive components into waste to be excreted.

Crohn’s disease, x-ray

Crohn's disease, x-ray

This lower abdominal x-ray shows narrowing (stenosis) of the end of the small intestine (ileum), caused by Crohn’s disease. Crohn’s disease typically affects the small intestine, whereas ulcerative colitis typically affects the large intestine. A solution containing a dye (barium), was swallowed by the patient. When it passed into the small intestines, this x-ray was taken (lower GI series).

Clubbing

Clubbing

Clubbing may result from chronic low blood-oxygen levels. This can be seen with cystic fibrosis, congenital cyanotic heart disease, and several other diseases. The tips of the fingers enlarge and the nails become extremely curved from front to back.

Inflammatory bowel disease

Inflammatory bowel disease

Crohn’s disease, also called regional enteritis, is a chronic inflammation of the intestines which is usually confined to the terminal portion of the small intestine, the ileum. Ulcerative colitis is a similar inflammation of the colon, or large intestine. These and other IBDs (inflammatory bowel disease) have been linked with an increased risk of colorectal cancer.

Anorectal fistulas

Anorectal fistulas

Crohn’s disease is an inflammation of the intestines caused by immune response to an infection. The lining of the intestine may ulcerate and form channels of infection, called fistulas. Fistulas tunnel from the area of ulceration, creating a hole which may continue until it reaches the surface of the organ, or the surface of nearby skin. These holes typically spread the infection that creates them, and life-threatening conditions such as peritonitis (inflammation of the lining of the abdomen) may occur.

Crohn’s disease – affected areas

Crohn's disease - affected areas

The inflammation of Crohn’s disease is nearly always found in the ileocecal region. The ileocecal region consists of the last few inches of the small intestine (the ileum), which moves digesting food to the beginning portion of the large intestine (the cecum). However, Crohn’s disease can occur anywhere along the digestive tract.

Ulcerative colitis

Ulcerative colitis

Ulcerative colitis is categorized according to location:

  • Proctitis involves only the rectum
  • Proctosigmoiditis affects the rectum and sigmoid colon
  • Left-sided colitis encompasses the entire left side of the large intestine
  • Pancolitis inflames the entire colon

Digestive system organs

Digestive system organs

The digestive system organs in the abdominal cavity include the liver, gallbladder, stomach, small intestine and large intestine.

Inflammatory bowel disease – series
Normal anatomy

Inflammatory bowel disease  - series : Normal anatomy

The gastrointestinal tract starts at the mouth, which leads to the esophagus, stomach, small intestine, colon, and finally, the rectum and anus. The GI tract is basically a long, hollow, muscular tube through which food passes and nutrients are absorbed.


Review Date : 10/18/2009
Reviewed By : David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc., and George F Longstreth, MD, Department of Gastroenterology, Kaiser Permanente Medical Care Program San Diego, California. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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