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.
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.
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.
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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