Inflammatory bowel disease (IBD) refers to a group of disorders that cause the intestines to become inflamed. IBD generally refers to chronic (long-lasting) inflammatory bowel diseases of unknown cause. IBD is typically diagnosed as either ulcerative colitis or Crohn's disease, depending on the depth of inflammation of the intestinal wall and the affected regions: ulcerative colitis affects the most superficial layer of the colon, called the mucosa, and the inflammation always involves the rectum * , whereas Crohn's disease affects all layers of intestinal tissue (transmural involvement) and may occur anywhere along the intestinal tract from lips to anus but most commonly occurs in the lower part of the small intestine (ileum).
IBD encompasses several disorders resulting in chronic inflammation * of the gastrointestinal tract. The different types of IBD have many symptoms in common, including abdominal pain, frequent diarrhea (sometimes with blood and mucus), constipation, weight loss, and fatigue. IBD is often associated with other inflammatory conditions, for example, fever, inflammation of the joints (arthritis), skin or eye lesions, and perianal disease * . There are many chronic inflammatory intestinal diseases, including those caused by bacteria (diverticulitis, chronic appendicitis, Helicobacter pylori gastritis), parasites (amoebic colitis, Giardia duodenitis), and physical and chemical agents (radiation enteritis, bile and peptic gastritis, and esophagitis), but the term IBD generally refers to chronic inflammatory bowel diseases of unknown cause.
What is known is that IBD is not passed from person to person. However, up to 25 percent of people with IBD have a relative with the disease, suggesting that genetic factors play a role in its development. Some researchers believe that IBD occurs because a virus or bacterium triggers an inappropriate response from the immune system * in people who have a genetic tendency for the disease. This abnormal response would then cause the digestive tract to become inflamed. But despite decades of study and searching for an infectious agent, as of 2015 none had been identified.
The two major types of IBD are ulcerative colitis and Crohn's disease. The disorders have many points in common: the cause of both IBDs remains unknown; they both have unpredictable outcomes; they have common symptoms, which are not necessarily intestinal; laboratory tests are inconclusive; and responses of patients to treatment vary.
Ulcerative colitis involves inflammation of the surface mucosal layer of the colon. The deeper or muscular and serosal layers of tissue are rarely affected. Inflammation always begins in the rectum. If the disease remains limited to this portion of the colon, then it is called ulcerative proctitis. But the disease often extends toward the small intestine for an unpredictable distance and then abruptly stops. Besides the affected segment, no other diseased regions occur that are separated by healthy tissue (“skip areas”), as are present in Crohn's disease. The inflammation typically involves only the mucosa * , with formation of ulcers.
These sores often result in bloody diarrhea, and substantial blood loss can occur. Ulcerative colitis affects only the rectum in approximately 25 percent of cases. It often spreads in continuous fashion to the more proximal large intestine. The small intestine is never involved, except when the ileum is temporarily inflamed. As the disease becomes chronic, the colon wall loses its undulations and starts looking like a lead pipe, as seen on imaging tests. In severe cases, it can extend to the submucosa * , but this is very rare.
Most people who develop ulcerative colitis are between the ages of 15 and 40 years, the most typical symptom being bloody diarrhea, accompanied by abdominal pain, cramping, and fever. The severity of the disease varies from person to person. Some people seldom have an attack of symptoms. Others have almost continuous attacks that interfere with their daily activities. One of the most serious complications of ulcerative colitis is “toxic megacolon,” which can lead to intestinal perforation, sepsis * , and death.
Experts agree that having ulcerative colitis increases the risk of intestinal cancer. Five percent of people with ulcerative colitis develop colon cancer. The longer a person has ulcerative colitis and the larger the affected region, the greater the risk of developing cancer. If only the lower colon and rectum are involved, the risk of cancer is the same as for the general population, but if the entire colon is affected, the risk of cancer becomes 32 times the normal rate. In some cases, cells lining the colon become precancerous, a condition referred to as dysplasia, which greatly increases the risk of cancer.
Crohn's disease (sometimes referred to as ileitis or enteritis) is an inflammation that extends deep into the tissues of the intestinal wall, unlike ulcerative colitis, which is only in the mucosa. Crohn's disease involves all layers of the bowel (transmural inflammation) and frequently involves the small intestine. Here it typically results in areas of marked thickening of the intestinal wall with multiple areas of narrowing resulting in obstruction of the passage of the intestinal contents. These areas may alternate with stretches of normal intestine. These normal areas are called skip areas. Crohn's disease affects the ileum and cecum * in 40 percent of patients, only the small intestine in 30 percent, and only the colon in 25 percent. Much less commonly, Crohn's disease can also affect the more central parts of the gastrointestinal tract, including the mouth, tongue, esophagus, stomach, and duodenum * . Perianal complications (fistulas * , fissures * , and abscesses * ) are common and coincide with the disease's characteristic transmural inflammation pattern.
There are many conflicting theories about what causes Crohn's disease. Men and women seem to be afliicted in equal numbers, and about 20 percent of people with the disease have a relative who also has it. Many people with Crohn's disease have weakened immune systems, but it is not known whether this is a cause or a result of the disease.
The most common complication of Crohn's disease is blockage of the intestine, because the intestinal walls tend to swell and thicken with scar tissue that eventually impairs the movement of intestinal contents. In some people, inflammation, perforation, and scarring extend into surrounding tissues, creating fistulas and a high risk of additional infection.
A medical history, physical examination, and diagnostic tests are required to diagnose IBD. Blood samples may be taken to search for evidence of anemia * and infection. Examination of stool samples for the presence of blood is also helpful in reaching a diagnosis.
Often the colon is examined through a procedure called a colonoscopy. An endoscope (a lighted flexible tube with a camera attached to a television monitor) is inserted through the anus. This procedure allows the doctor to see the inside lining of the colon and rectum. Sometimes during the colonoscopy, a tissue sample (called a biopsy) is taken from the intestinal lining for further examination under a microscope.
Another diagnostic procedure commonly used is a barium study. A person drinks a mixture of barium that is flavored with another liquid, and then the person is x-rayed. Because barium shows up on x-rays, the doctor can detect abnormalities as the mixture flows through the person's intestines. CT scans * may be useful in evaluating the progress of the disease once it has been diagnosed.
However, invasive procedures such as endoscopies and barium x-rays can be contraindicated during the acute phase of IBD, as they carry the risk of perforating the intestinal wall, which is weakened by inflammation.
Because ulcerative colitis and Crohn's disease often have different complications, they also have distinct medical and surgical treatments aimed at relieving specific symptoms.
Medication and diet are the two primary approaches to controlling IBD. They do not cure the disease but are effective in reducing symptoms in the majority of people. In severe cases of IBD, surgery may be necessary. Anti-inflammatory drugs often are used to help control the inflammation. In some cases, immunosuppressant drugs may be helpful in controlling symptoms that do not respond to anti-inflammatory drugs. Antibiotics are also used to treat Crohn's disease. Several experimental drug therapies were under investigation as of 2015.
Many of the drugs used to treat IBD are powerful and may have undesirable side effects. The physician must balance the undesirable side effects against the positive benefits, sometimes trying several different drug combinations before a successful balance is reached.
In addition to drug therapy, a special diet may be prescribed. Because IBD interferes with nutrition, people with the disease often must increase the amount of calories, vitamins, and minerals they consume. Some individuals find that they must avoid specific foods that aggravate their symptoms. Other people find that a bland, low-fiber diet offers some relief. Because there is no cure for IBD and because the diseases are unpredictable in their course, people with any form of the disease should receive regular medical examinations that include a review of their treatment and diet.
About 70 percent of people with Crohn's disease eventually need to have damaged areas of the intestine removed. Removing the damaged parts does not cure the disease, because the inflammation may return in other places in the intestine, usually near the surgical site. Many people with Crohn's disease need additional surgeries. Multiple surgical resection can lead to short bowel syndrome. Surgery may be necessary to remove or open narrowed areas causing obstruction. Surgery may be required for the removal and healing of fistulae.
Extensive Crohn's disease may require intravenous feeding to assure normal growth and development in children.
People with IBD often go for substantial periods when they feel well and have few symptoms. During these times, they are able to hold jobs, raise families, and participate in normal daily activities. Throughout the United States, there are support groups for people with IBD that help them learn to cope with their illness and maintain a normal, happy life.
Nevertheless, IBD is very frequently a difficult problem, producing both physical and emotional stresses. Comprehensive care should always offer patients with these problems knowledgeable and sensitive professional services. Addressing these issues is time-consuming yet essential.
See also Colorectal Cancer • Constipation • Crohn's Disease • Diarrhea • Diverticulitis/Diverticulosis • Irritable Bowel Syndrome
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* rectum is the final portion of the large intestine, connecting the colon to the outside opening of the anus.
* inflammation (in-fla-MAY-shun) is the body's reaction to irritation, infection, or injury that often involves swelling, pain, redness, and warmth.
* perianal disease affects the regions around the anus.
* immune system (im-YOON SIStem) is the system of the body composed of specialized cells and the substances they produce that help protect the body against disease-causing germs.
* mucosa (mu-KOH-sa) is the moist tissue that lines some organs and body cavities. It makes mucus, which is a thick, slippery fluid.
* submucosa (sub-mu-KOH-sa) is the layer of tissue under the mucosa.
* sepsis is a potentially serious spreading of infection, usually bacterial, through the bloodstream and body.
* cecum (SEE-kum) is the pouchlike start of the large intestine that connects it to the small intestine.
* duodenum (dew-eh-DEE-num) is the first part of the small intestine that connects to the stomach.
* fistulas (FIS-tu-las) are abnormal connections between two organs or leading from an internal organ to the surface of the body.
* fissures are tears in tissue.
* abscesses (AB-seh-sez) are localized or walled-off accumulations of pus caused by infection that can occur anywhere within the body.
* biopsies (BI-op-seez) are tests in which small samples of skin or other body tissue are removed and examined for signs of disease.
* anemia (uh-NEE-me-uh) is a blood condition in which there is decreased hemoglobin in the blood and, usually, fewer than normal numbers of red blood cells.
* CT scans, computed tomography (to-MOG-ra-fee) scans, or CAT (computerized axial tomography) scans, use computers to view structures inside the body.
* colostomy (ko-LOS-to-mee) is a surgical procedure in which a part of the large intestine is removed, and the end of the intestine is attached to an opening made in the abdomen. he stool is passed through this pening into a special bag.