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.
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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 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 aminosalicylates (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.
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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 aminosalicylates (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.
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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 younger than 18 years. 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.1
Precise incidence and prevalence of Crohn’s disease and ulcerative colitis have 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.2 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 more prevalent among ex-smokers and nonsmokers, whereas Crohn’s disease is more prevalent among smokers.
- There have been three studies outside of the United States that specifically examined the relationship between socioeconomic factors and IBD. One study found both ulcerative colitis and Crohn’s disease more prevalent in white collar compared with blue-collar occupations.3 Bernstein (2001) found Crohn's disease and ulcerative colitis less common in higher SES groups and Li (2009) found a minor association between specific occupations and IBD in a hospital-based study.4,5 This relationship should be further investigated in a U.S. population.
- 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, variances in exposure to sunlight, pollution, and industrial chemicals.6
- Other factors such as diet, oral contraceptives, perinatal and childhood infections, or atypical mycobacterial infections have been suggested but not proven to play a role in expression of IBD.7
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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 more than 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.3
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1 Loftus EV. Clinical epidemiology of inflammatory bowel disease: incidence, prevalence, and environmental influences. Gastro May 2004;126(6):1504–17.
2 Lakatos PL. Recent trends in the epidemiology of inflammatory bowel diseases: up or down? World J Gastroenterol 2006;12(38):6102–08.
3 Sonnenberg A. Disability from inflammatory bowel disease among employees in West Germany. Gut. 1989;30(3):367–70.
4 Bernstein CN, Kraut A, Blanchard JF, Rawsthorne P, Yu N, Walld R. The relationship between inflammatory bowel disease and socioeconomic variables.
Am J Gastroenterol 2001;96(7):2117–25.
5 Li X, Sundquist J, Sundquist K. Educational level and occupation as risk factors for inflammatory bowel diseases: a nationwide study based on hospitalizations in Sweden. Inflamm Bowel Dis 2009;15(4):608–15.
6 Hanauer S. Inflammatory Bowel Disease: epidemiology, pathogenesis and therapeutic opportunities. Inflamm Bowel Dis 2006;12:S3-9 (Suppl 1).
7 Feldman M, Friedman LS, Brandt LJ, editors. Sleisenger and Fordtran's Gastrointestinal and Liver Disease: Pathophysiology, Diagnosis, and Management 8th edition. Philadelphia, PA: Publisher Saunders an imprint of Elsevier; 2006.
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