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Gastrointestinal Diseases at a Glance

Inflammatory Bowel Disease (IBD), Crohn's Disease, Ulcerative Colitis, Spastic Colon

What is IBD?

Inflammatory Bowel Diseases (IBD) is a broad term that describes conditions with chronic or recurring immune response and inflammation of the gastrointestinal tract. The two most common inflammatory bowel diseases are ulcerative colitis and Crohn's disease.

Both illnesses have one strong feature in common. They are marked by an abnormal response by the body's immune system. Normally, the immune cells protect the body from infection. In people with IBD, however, the immune system mistakes food, bacteria, and other materials in the intestine for foreign substances and it attacks the cells of the intestines. In the process, the body sends white blood cells into the lining of the intestines where they produce chronic inflammation. When this happens, the patient experiences the symptoms of IBD.

Neither ulcerative colitis nor Crohn's disease should be confused with irritable bowel syndrome (IBS), a disorder that affects the motility (muscle contractions) of the colon. Sometimes called "spastic colon" or "nervous colitis," IBS is not characterized by intestinal inflammation. It is, therefore, a much less serious disease than ulcerative colitis or Crohn's disease. IBS bears no direct relationship to either ulcerative colitis or Crohn's disease.


Inflammatory Bowel Disease (IBD) Causes, Symptoms, Treatment See Slideshow

About Crohn's Disease

Crohn's disease is a condition of chronic inflammation potentially involving any location of the gastrointestinal tract, but it frequently affects the end of the small bowel and the beginning of the large bowel. 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.

Symptoms include persistent diarrhea (loose, watery, or frequent bowel movements), cramping abdominal pain, fever, and, at times, rectal bleeding. Loss of appetite and weight loss also may occur. However, the disease is not always limited to the gastrointestinal tract; it can also affect the joints, eyes, skin, and liver. Fatigue is another common complaint.

The most common complication of Crohn's disease is blockage of the intestine due to swelling and scar tissue. Symptoms of blockage include cramping pain, vomiting and bloating. Another complication is sores or ulcers within the intestinal tract. Sometimes these deep ulcers turn into tracts—called fistulas. In 30% of people with Crohn's disease, these fistulas become infected. Patients may also develop a shortage of proteins, calories, or vitamins. They generally do not develop unless the disease is severe and of long duration. Until recently an increased risk of cancer was thought to exist mainly for ulcerative colitis patients, but it is now known that Crohn's patients have an increased risk of colon cancer as well.

The five groups of drugs used to treat Crohn's disease today are aminosaliclylates (5-ASA), steroids, immune modifiers (azathioprine, 6-MP, and methotrexate), antibiotics(metronidazole, ampicillin, ciprofloxin, others) and biologic therapy (inflixamab). Two-thirds to three-quarters of patients with Crohn's disease will require surgery at some point during their lives. Surgery becomes necessary in Crohn's disease when medications can no longer control the symptoms.

About Ulcerative Colitis

Ulcerative colitis is a chronic gastrointestinal disorder that is limited to the large bowel (the colon). Ulcerative colitis does not affect all layers of the bowel, but only affects the top layers of the colon in an even and continuous distribution. The first symptom of ulcerative colitis is a progressive loosening of the stool. The stool is generally bloody and may be associated with cramping abdominal pain and severe urgency to have a bowel movement. The diarrhea may begin slowly or quite suddenly. Loss of appetite and subsequent weight loss are common, as is fatigue. In cases of severe bleeding, anemia may also occur. In addition, there may be skin lesions, joint pain, eye inflammation, and liver disorders. Children with ulcerative colitis may fail to develop or grow properly.

Approximately half of all patients with ulcerative colitis have mild symptoms. However, others may suffer from severe abdominal cramping, bloody diarrhea, nausea, and fever. The symptoms of ulcerative colitis do tend to come and go, with fairly long periods in between flare-ups in which patients may experience no distress at all.

Complications of ulcerative colitis are less frequent than in Crohn's disease. Complications can include bleeding from deep ulcerations, rupture of the bowel or failure of the patient to respond to the usual medical treatments. Another complication is severe abdominal bloating. Patients with ulcerative colitis are at increased risk of colon cancer.

The four major classes of medication used today to treat ulcerative colitis are: aminosaliclylates (5-ASA), steroids, immune modifiers (azathioprine, 6-MP, and methotrexate) and antibiotics (metronidazole, ampicillin, ciprofloxin, others). In one-quarter to one-third of patients with ulcerative colitis, medical therapy is not completely successful or complications arise. Under these circumstances, surgery may be considered. This operation involves the removal of the colon (colectomy). Unlike Crohn's disease, which can recur after surgery, ulcerative colitis is "cured" once the colon is removed.


What is Crohn's disease? See Answer

Epidemiology of IBD

The peak age of onset for IBD is 15 to 30 years old, although it may occur at any age. About 10% of cases occur in individuals less than 18 years old. Ulcerative colitis is slightly more common in males, whereas Crohn's disease is marginally more frequent in women. IBD occurs more in people of Caucasian and Ashkenazic Jewish origin than in other racial and ethnic subgroups. In the past, it was thought that IBD occurred less frequently in ethnic or racial minority groups compared with whites. But, previously noted racial and ethnic differences seem to be narrowing.

Precise incidence and prevalence of Crohn's disease and ulcerative colitis has been limited by (1) a lack of gold standard criteria for diagnosis; (2) inconsistent case ascertainment; and (3) disease misclassification. The data that does exist suggest that the worldwide incidence rate of ulcerative colitis varies greatly between 0.5-24.5/100,000 persons, while that of Crohn's disease varies between 0.1-16/100,000 persons worldwide, with the prevalence rate of IBD reaching up to 396/100,000 persons.  It is estimated that as many as 1.4 million persons in the United States suffer from these diseases.

The etiology of IBD is unknown but is thought to involve genetic, immunologic and environmental factors as evidenced by the following:

  • The greatest relative risk of IBD disease is found among first-degree relatives, suggesting a strong genetic component.
  • Smoking is one of the more notable environmental factors. Ulcerative colitis is largely a disease of ex-smokers and nonsmokers, whereas Crohn's disease is more prevalent among smokers.
  • Both ulcerative colitis and Crohn's disease are more prevalent in white collar compared with blue-collar occupations. It has been suggested that a work environment involving outdoor air and physical activity is protective against IBD, whereas work in artificial venues confers an increased risk.
  • IBD is more common in developed countries. There is a noted north- to- south variation and higher frequency in urban communities compared with rural areas. These observations suggest that urbanization is a potential contributing factor. It is postulated that this is the result of “westernization” of lifestyle, such as changes in diet, smoking and variances in exposure to sunlight, pollution and industrial chemicals.
  • Other factors such as diet, oral contraceptives, perinatal/childhood infections or atypical mycobacterial infections have been suggested but not proven to play a role in expression of IBD.

Impact of the IBD as a Chronic Disease

IBD is one of the five most prevalent gastrointestinal disease burdens in the United States, with an overall health care cost of more than 1.7 billion. This chronic condition is without a medical cure and commonly requires a lifetime of care. Each year in the United States, IBD accounts for over 700,000 physician visits, 100,000 hospitalizations, and disability in 119,000 patients. Over the long term, up to 75% of patients with Crohn's disease and 25% of those with ulcerative colitis will require surgery.

Current CDC IBD Activities

CDC uses collaborations and resources to help better define and understand IBD.

  • CDC scientists and epidemiologists provide technical expertise to extramural researchers and fund pilot projects to describe the epidemiology and causes of IBD, including both Crohn's disease and ulcerative colitis.
  • CDC, in collaboration with a nationwide geographically diverse network of large managed health care delivery systems, supports an epidemiological study of IBD to understand IBD incidence, prevalence, demographics and healthcare use. The Crohn's and Colitis Foundation of America implemented the extramural activities of this 3-year epidemiology collaboration. This study found an average annual incidence rate of 8.4 per 100,000 people for Crohn's disease and 12.4 per 100,000 for ulcerative colitis (unpublished data).
  • During the initial 3-year epidemiologic collaboration, CDC laboratory workers and epidemiologists worked to improve detection tools and epidemiologic methods to study the role of infections (infectious disease epidemiology) in pediatric IBD, collaborating with extramural researchers who were funded by an NIH R03 research award. A senior CDC medical epidemiologist also served as adviser on other epidemiologic and causation studies conducted by the multi-region consortium of pediatric IBD gastroenterologists
  • In FY 2006 and FY2007, CDC epidemiologists are working in conjunction with the Crohn's and Colitis Foundation and a large health maintenance organization to better understand the natural history of IBD and factors that predict the course of disease. The current study will address questions regarding practice variation such as variability in quality of treatment given to patients with IBD in the community setting; patient, provider, or clinic predictors of treatment variability; and possible effects of this variability, if any, on patient outcomes.



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PL Lakatos. Recent trends in the epidemiology of inflammatory bowel diseases: Up or down? World J Gastroenterol 2006 October 14;12(38): 6102–6108.

S Hanauer. Inflammatory Bowel Disease: Epidemiology, pathogenesis and therapeutic opportunities. Inflamm Bowel Dis Jan 2006;12, Suppl 1.

Sleisenger & Fordtran's gastrointestinal and liver disease : pathophysiology, diagnosis, management / [edited by] Mark Feldman, Lawrence S. Friedman, Lawrence J. Brandt.—8th ed. Publisher Saunders an imprint of Elsevier, Philadelphia, PA . Printed in Canada 2006.


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