Inflammatory bowel disease (IBD) refers to two different chronic conditions or diseases that may be related, Crohn's disease and ulcerative colitis. Both diseases consist of inflammation of the wall of the bowel or intestines - hence the name - leading to bowel that is inflamed, swollen and that develops ulcers. The inflammation and its consequences are different in Crohn's disease and ulcerative colitis. The inflammation results in various degrees of abdominal discomfort, diarrhea, and intestinal bleeding. Both diseases can result in serious digestive problems.
In Crohn's disease, inflammation involves the entire wall of the bowel, even the deeper portions. It may involve any part of the digestive tract from the mouth to the colon, rectum, and anus, although the small intestine, particularly the ileum, is the most commonly involved organ with the colon the next most commonly involved organ. One of the characteristics of Crohn's disease is that involvement of the bowel may be discontinuous, that is, several areas may be inflamed but intervening segments may be normal.
Unlike Crohn's disease, in ulcerative colitis the inflammation involves only the superficial layers of the wall of the bowel, the innermost lining. Involvement is limited to the colon and rectum without skipped areas. Inflammation may be limited to the rectum (referred to as ulcerative proctitis), but usually is more extensive, extending variable distances to involve the sigmoid, descending, transverse, and ascending colon.
Although the symptoms of Crohn's disease and ulcerative colitis are similar, they are not identical. Abdominal pain and diarrhea are common to both diseases as is loss of weight and fever. Ulcerative colitis tends to be associated with more bleeding due to the extensive erosion by inflammation of the blood vessels supplying the lining of the colon. On the other hand, symptoms of obstruction of the bowel (pain, nausea and vomiting, and abdominal distension) are more common in Crohn's disease because the entire wall of the bowel is inflamed. The more extensive inflammation causes more swelling than the superficial inflammation of ulcerative colitis that can obstruct the flow of digesting food through the bowel.
Manifestations of IBD may occur outside the digestive tract. Several types of skin conditions (erythema nodosum, pyoderma gangrenosum) are seen as is uveitis, an inflammation of the eye that can affect vision. Arthritis, including sacroiliitis of the pelvis, may occur. More serious but less common is sclerosing cholangitis, an inflammation of the bile ducts draining the liver. Although each manifestation can occur in either Crohn's disease or ulcerative colitis, in general, each manifestation is more common in one or the other disease. For example, sclerosing cholangitis is much more common in ulcerative colitis than Crohn's disease.
The cause of IBD is unknown. What is known is that a combination of genetic and environmental factors results in ongoing inflammation localized mostly to the bowel that for some reason is not controlled. The continuing inflammation results in the local destruction of the bowel as well as manifestations outside of the bowel. Therefore, treatments are directed towards controlling the inflammation.
IBD occurs equally in men and women. Although it usually begins during the teens or early adulthood, it may develop at other times, even among infants and the elderly. Early observations were made that relatives of patients with IBD were approximately 10 times more likely to have IBD (usually the same type as the patient, i.e., either Crohn's disease or ulcerative colitis). If the patient is a twin, the other twin is even more likely to have IBD, and identical twins are more likely to share IBD than even fraternal twins. IBD is more common among Caucasians and people of Jewish descent.
IBD is sometimes confused with irritable bowel syndrome (IBS). The cause of IBS, as for IBD, is not known. The striking difference between the two diseases is that there is no identifiable inflammation in IBS. Some symptoms may be similar - abdominal pain, diarrhea - but the other symptoms and signs of IBD are not seen - bloody stools, fever, and weight loss. The cause of IBS is believed to be dysfunction of the intestinal muscles, nerves, and secretions and not inflammation. Signs of inflammation in the intestine as well as symptoms outside of the abdomen are not seen in IBS.
The bowel has only a few ways in which it can respond to diseases that affect it, so it is not surprising that the symptoms of IBD can overlap with other intestinal diseases. The similarity of some symptoms with IBS already has been mentioned. Other common abdominal diseases that can mimic IBD are diverticulitis, celiac disease, and colon cancer.
Although to a large extent replaced by endoscopy, barium X-ray studies still are used for the diagnosis of IBD. In the case of ulcerative colitis, the barium enema examination is most helpful since it examines the colon. In Crohn's disease the small bowel series is most helpful since the small bowel is where the disease most commonly occurs. These X-ray studies can identify ulcerations, narrowing and skipped areas, which can help to differentiate Crohn's disease from ulcerative colitis.
Endoscopy is the best method for diagnosing IBD. Among endoscopic procedures, colonoscopy is most effective since it can examine the entire colon as well as the terminal ileum and is able, therefore, to diagnose most cases of Crohn's disease and ulcerative colitis. Colonoscopy is able to recognize more subtle signs of inflammation than barium studies, and also provides the opportunity to biopsy the lining of the colon and ileum. Biopsies can be useful in differentiating between Crohn's disease and ulcerative colitis and also differentiating these diseases from other less common inflammatory diseases of the bowel. When Crohn's disease affects the small bowel, but not the terminal ileum, the colonoscope may not be able to reach the involved area of the small intestine. In this situation, enteroscopy, a type of endoscopy, or a swallowed video capsule, both of which examine the small bowel, can be used.
Most patients with IBD have their treatment managed by subspecialists in internal medicine who specialize in digestive disorders known as gastroenterologists. Referral to centers may be necessary for specialized procedures such as small bowel enteroscopy and video capsule studies. Referral to centers also may be necessary if a patient's clinical course is complex or severe or the patient may be a good candidate for trials of experimental drugs.
There is a great range in the severity of the symptoms of IBD, and the severity may vary over time even without a change in treatment. Long periods of months to years may occur with minimal symptoms, referred to as remissions. Remissions may be followed by episodes of increased symptoms, referred to as flares that may require temporary or prolonged changes in treatment. In ulcerative colitis, only 5% to 10% of patients have symptoms all of the time. Interestingly, even when there are minimal symptoms, colonoscopy and biopsy may show continued inflammation though the inflammation usually is of a milder degree than the inflammation seen during a flare.
Stress makes almost every symptom of every disease seem worse, but it is a cause of vary few diseases. The situation is the same in IBD. Stress makes the symptoms seem worse, and unfortunately, stress is a part of most peoples' lives. Therefore, it is likely just by chance alone that a period of stress may precede a flare of IBD, Although it is possible that stress, because it causes many hormonal and neurological changes, may actually increase the degree of inflammation in IBD or at least the perception of symptoms, there is no proof of this. Stress does not cause IBD, but it always is reasonable to reduce stress during flares if possible.
The inflammation of Crohn's disease involves the full thickness of the bowel wall. There is a lot of swelling that occurs with the inflammation. The swelling can narrow the lumen (passage) within the intestine. In addition, part of the inflammatory process is the laying down of scar tissue. Once scar tissue is laid down, it contracts and a stricture is formed. In the bowel, this contraction also can result in a narrowing of the lumen. Whether by inflammation or the formation of scar tissue, the narrowing of the bowel can obstruct the flow of bowel contents. The contents back up and lead to bowel distension and pain, nausea, and vomiting. The abdomen often becomes swollen due to the distended bowel and secretion of intestinal fluids. Eventually, the bowel may cease to function altogether (ileus). Obstruction usually is treated in the hospital with treatment directed at either the inflammation, the scar tissue, or both.
Crohn's disease, because of its characteristic involvement of the full thickness of the bowel wall, can lead to deep ulcers which can turn into abscesses, pockets of infected pus, causing pain and fever of even obstruction of the bowel. The infection can spread throughout the body (sepsis). The ulcer also may penetrate the bowel wall and enter other nearby organs, for example, the urinary bladder or the vagina. The fistulas also may erode through the skin to the outside of the body. The resulting tracts from the bowel to the organs and skin are known as fistulas. Such fistulas may result in chronic bladder infections or drainage of bowel contents into the bladder and vagina. Fistulas and abscesses usually are treated surgically, though some of the more potent treatments for Crohn's disease may allow fistulas to heal spontaneously without specific treatment.
Cancer of the bowel is a later complication of IBD. It is more common in ulcerative colitis than Crohn's disease, and much more commonly involves the colon. The risk of colon cancer begins to increase after eight years of disease and increases in frequency with increasing extent of inflammation. Thus, patients with colitis involving the entire colon are more likely to develop cancer. Endoscopic screening for colon cancer in ulcerative colitis usually is recommended. It is important to remember, however, that the vast majority of patients with IBD do not get colon cancer.
The inflammation of IBD involves the bowel, the primary digestive organ. It is not surprising; therefore, that IBD has effects on the digestion of food (for example, maldigestion and some vitamin deficiencies). It is not clear, however, whether the reverse is true, i.e., that foods have an effect on IBD. It is generally recommended that patients eliminate foods that seem to aggravate their symptoms, though there are no foods that should be specifically prohibited. It is reasonable to test for the effects of milk on symptoms since the symptoms of lactose intolerance (a common problem) can aggravate the diarrhea of IBD. However, if there is no intolerance to lactose, continued elimination of milk is unnecessary. Gas-forming foods such as beans also may aggravate abdominal symptoms.
A low residue (fiber) diet often is prescribed for patients with Crohn's disease on the assumption that if there is less indigestible matter, there will be less bulk within the bowel, and the contents of the bowel will pass more easily particularly if the bowel is narrowed. Since the contents of the small intestine are already in liquid form and should pass easily even through narrowed areas, it is not clear whether reducing bulk is important. If a low residue diet is prescribed, it probably should be prescribed only during flares. If there is concern about major obstruction, a liquid or even clear liquid diet may be a better choice.
If Crohn's disease involves a large portion of the small intestine or surgery has removed a large portion, there may be malabsorption of vitamins and/or minerals, particularly those absorbed primarily from the terminal ileum (for example, vitamin B12), a section of bowel that is frequently diseased or removed in patients with Crohn's disease. To avoid deficiencies, supplemental vitamins and minerals often are prescribed as is a well-balanced diet. To accomplish the latter, it may be helpful to consult a dietician. Loss of weight also may occur if disease or resection is extensive enough to reduce the absorption of fat and protein. Loss of weight and vitamin or mineral deficiencies also may occur because of a poor appetite or the provocation of symptoms by eating. Caloric supplements may be necessary.
As previously discussed, reduction of stress may improve symptoms of IBD or at least their perception, but probably does not affect the underlying inflammation. Individual or group therapy may help to reduce stress as may yoga, meditation, or exercise.
Treatment of IBD depends on the type of IBD - Crohn's disease or ulcerative colitis - the location and extent of the disease, and the severity of the disease. For mild disease activity, anti-inflammatory drugs (aminosalicylates) that work locally on the bowel may be used either orally or as enemas. For moderate activity, particularly during flares, corticosteroids, another type of anti-inflammatory drug may be used either orally or by enema or even by injection. More severe activity is treated with other types of drugs that also target inflammation, the immunomodulators and biologics.
Two types of medications are used for more severe IBD or IBD that is unresponsive to other medications. One type of drug includes immunomodulators, drugs that reduce the activity of the immune system and thereby inhibit the stimulus provided by the immune system that causes inflammation. The second type of drug includes what is referred to as biologics. Biologics are man-made antibodies that block the action of some of the protein molecules released by the immune system that stimulate inflammation and injure cells. Immunomodulators are used both in Crohn's disease and ulcerative colitis. Biologics are mostly used in Crohn's disease. In Crohn's disease, a combination of immunomodulator and biologic drugs seem to be particularly effective.
Patients with IBD commonly undergo surgery. In ulcerative colitis, surgery may be used for treating severe disease, disease that does not respond to treatment, and to prevent the development of cancer. Almost always, the entire colon is removed since ulcerative colitis frequently involves the entire colon and can spread to other uninvolved parts of the colon after the diseased part is removed. Whereas in the past removal of the colon meant that patients would need a bag to collect the small intestinal contents directly, it is now possible to surgically create a reservoir for the contents out of small intestine and allow patients to have normal bowel movements.
Surgery in ulcerative colitis has a major benefit; it cures the disease since it removes the entire organ (the colon) that can be involved. In Crohn's disease, surgery also may be used for treating severe or unresponsive disease, but usually is performed for complications of the disease such as fistulas and strictures. Surgery rarely cures Crohn's disease because of the tendency for inflammation to return in new sections of the bowel after the diseased portions are removed.
Exercise and other stress-reducing activities such as yoga, meditation, or tai chi promote feelings of well being and by reducing stress may reduce the perceived severity of symptoms.
IBD often is a lifelong disease; except for individuals who have their colons removed for ulcerative colitis and are cured of their disease. Appropriate and adequate treatment is critical, but because of the relapsing nature of the disease, it is important to learn how to deal with the flares with lifestyle changes, and stress management. The goal is to keep the symptoms from interfering with day-to-day life.
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