Inflammatory bowel disease (IBD) refers to a group of inflammatory disorders of all or part of the digestive tract, including the small intestine and large intestine. The two main types of IBD are ulcerative colitis and Crohn's disease, which cause the intestines to become inflamed. Symptoms of IBD can be painful and debilitating, and in some instances lead to serious complications, including the need for surgery.
Although ulcerative colitis and Crohn's disease have some features in common, they have some important differences.
Crohn's disease (CD) involves ongoing (chronic) inflammation of the gastrointestinal tract, from the mouth to the anus, with ulceration and formation of fistulas and perianal abscesses. Five types are recognized, depending on the affected region:
Ulcerative colitis typically involves continuous inflammation from the rectum to the entire colon. The disease usually begins in the rectal area and may eventually spread to the entire large intestine. Repeated inflammation thickens the wall of the intestine and rectum with scar tissue.
More than 600,000 Americans are diagnosed every year with some type of inflammatory bowel disease. Ulcerative colitis may affect any age group, although peaks occur at ages 15–30 and 50–70. Crohn's disease may occur at any age, but it commonly affects people between the ages of 15 and 35. Risk factors include a family history of Crohn's disease, Jewish ancestry, and smoking tobacco products. Men and women appear to be at equal risk of developing IBD. According to the Crohn's and Colitis Foundation of America, two-thirds to three-quarters of patients with Crohn's disease will need bowel surgery at some point.
A large study conducted from 1976 to 2003 and published in 2012 in the journal Gut (“Geographical Variation and Incidence of Inflammatory Bowel Disease among US Women”) found that women were less at risk for developing IBD if they lived in a sunny climate. More than 238,000 women in the United States participated in the study, called the Nurses' Health Study. Data and medical records were collected on the participants at birth, at age 15 years, and at age 30 years.
The U.S. study, conducted by American gastroenterologist Hamed Khalilil (Massachusetts General Hospital, Boston) and fellow Massachusetts colleagues, concluded that women in southern climates, which receive more sunlight than northern ones, had a 52% lower risk of being diagnosed with Crohn's disease and a 38% lower risk of developing ulcerative colitis by age 30 than women living in northern latitudes. The study results were in line with research done in Europe and suggest that sun exposure may play a role in IBD development, although further research is needed to examine this relationship.
The exact causes of IBD are unknown. The disease may be caused by a germ or by an immune system problem. It is known that IBD is not contagious, and it seems to be hereditary. In the case of ulcerative colitis, symptoms vary in severity and may start gradually or suddenly. They usually include all or some of the following:
The exact cause of Crohn's disease is also unknown, but it has been linked to a problem with the body's immune system (autoimmune disease). The immune system helps protect the body from harmful foreign substances and pathogens. In patients with Crohn's disease, the immune system cannot distinguish between the body's own cells and foreign invaders. The result is an overactive immune response that leads to chronic inflammation. Because Crohn's disease can affect any part of the gastrointestinal tract, symptoms can vary greatly between affected individuals. The following may be observed:
Based on a careful history of symptoms, the examining physician distinguishes between Crohn's disease and ulcerative colitis. Diagnosis can be difficult, however, because other diseases have IBD-like symptoms. For example, Crohn's disease, because it can affect various regions of the gastrointestinal tract, is commonly misdiagnosed as celiac disease or diverticulitis. To help ensure correct diagnoses, physicians may use additional tests, such as:
The primary goal of IBD treatment is to control inflammation and reduce the symptoms of pain, diarrhea, and bleeding when present. Many types of medicine can reduce inflammation, including anti-inflammatory drugs such as sulfasalazine (Azulfidine), corticosteroids such as prednisone, and immune system suppressors such as azathioprine (Imuran) and mercaptopurine (Purinethol). An antibiotic, such as metronidazole (Flagyl), may also be helpful in destroying germs in the intestines, especially for Crohn's disease. Antidiarrheal medications, laxatives, or pain relievers may also be prescribed. If symptoms are severe, such as diarrhea, fever, or vomiting, hospitalization may be required to administer intravenous fluids and medicines.
In the case of severe ulcerative colitis that cannot be helped by medications, a type of surgery called bowel resection may be performed to remove a damaged part of the intestine or to drain an abscess. If a part of the bowel is removed, a procedure is done to connect the remaining two ends of the bowel (anastomosis). In very severe cases, removal of the entire large intestine (colectomy) is required. Bowel resections may also be performed for Crohn's disease patients.
Diet is an essential component of IBD treatment and management. Eating a diet sufficient in energy and balanced in macronutrients and essential micronutrients is important to avoid malnutrition and weight loss. Although no clear evidence indicates that specific foods directly cause or improve Crohn's disease, some people find that some foods seem to trigger or worsen their symptoms. Foods that increase diarrhea should also be avoided. People who experience blockage of the intestines may need to avoid raw fruits and vegetables. Those who have difficulty digesting lactose (a condition known as lactose intolerance) also need to avoid milk products or reduce their intake. Some people can tolerate fermented products such as yogurt and cheese. If not, calcium-fortified soy milk may be substituted. Drinking plenty of fluids (8–10 servings daily) will help to keep the body hydrated and prevent constipation.
Eating a high-fiber diet may help manage symptoms when IBD is under control (in remission). High-fiber foods include:
During an IBD attack, however, a high-fiber diet may worsen symptoms, while low-residue diets may help give the bowel a rest and minimize symptoms. A low-residue diet includes:
Foods that should be avoided during IBD flareups include:
Some studies suggest that fish oil and flaxseed oil may be helpful in managing IBD. Recent studies also suggest that probiotics and prebiotics such as psyllium, a soluble fiber that comes from a plant called Plantago afra, can play a role in the healing process. These may also be helpful in allowing the intestines to recover. A 2017 study found that supplemental psyllium fibre improved the intestinal barrier and reduced inflammation in mice.
In the 2010s, experts found that restricting fermentable oligosaccharides, disaccharides, monosacharides, and polyols (FODMAPs) was an effective method of treating irritable bowel syndrome, and, although there has so far been no evidence to suggest that a low-FODMAP diet can help with IBD, some patients have experimented with it. FODMAPs are short-chain carbohydrates. Humans lack the enzymes to digest these carbohydrates so they are not fully absorbed in the small intestine, and instead drag water into the intestine where it can ferment and generate gases. Foods high in FODMAPs include wheat, rye, barley, onion, garlic, cruciferous vegetables such as cabbage and brussels sprouts, cauliflower, asparagus, beans, many fruits, and artificial sweeteners such as sorbitol, xylitol, mannitol, and isomalt. Foods low in FODMAPs include meats, tofu, almonds and seeds, oranges, grapes, melons, hard cheeses, vegetables including lettuce, tomato, zucchini, bean sprouts and alfalfa sprouts, carrots, and cucumbers. Lactose-free dairy products and gluten-free breads and baked goods are also low in FODMAPs.
The management of IBD depends on the type diagnosed, and pharmacologic and other therapies are tailored accordingly to individual cases, depending on severity and patient history. Therapeutic agents are carefully selected based on symptom severity and drug side effects. Because IBD is a chronic illness with an important and unpredictable impact on an individual's life, effective therapy usually requires much more than the initial treatment of symptoms. Patient cooperation is crucial for improvement, as dietary and lifestyle changes have been shown to be beneficial. Whatever the symptoms, patients also need to get enough rest while learning to manage the stress in their lives, as intestinal problems tend to be worse in overly stressed people. The Crohn's and Colitis Foundation of America (CCFA) can provide patient information on IBD and support groups that can often help with the stress of dealing with IBD, with useful tips for finding the best treatment and coping with the disease.
The outcome of ulcerative colitis is variable. It may be dormant and then worsen over a period of years, or it may progress quickly. The risk of colon cancer increases after ulcerative colitis is diagnosed.
No cure has been found for Crohn's disease, but it is not a deadly illness. Periods of improvement are often followed by flare-ups of symptoms. People with Crohn's disease have an increased risk of small bowel or colorectal cancer.
See also Anti-inflammatory diets ; Constipation ; Crohn's disease ; Digestive diseases ; Glucosamine ; Gut microbiota ; High-fiber diet ; Irritable bowel syndrome ; Irritable bowel syndrome diet ; Macronutrients ; Malnutrition ; Prebiotics and probiotics .
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Monique Laberge, PhD
Revised by Amy Hackney Blackwell, PhD